Arxiu de la categoria: HUMAN EVOLUTION

Ötzi, the ice mummy, is still fascinating

Ötzi is the oldest human mummy known and one of the most studied by science. It was discovered in 1991 in the Alps and since then it has not stopped leaking information about what life was like in the Neolithic. Do you dare to find out all its secrets?

WHAT IS A MUMMY?

Mummies are preserved bodies of people and animals that still preserve their skin. The most famous are the Egyptian ones, preserved thanks to the chemical processes applied to the corpses (embalming), although many other cultures practiced mummification. But mummies can also occur naturally if the conditions are suitable to avoid decomposition, such as humid and swampy sites, in the cold of mountains and polar regions or in dry and sandy areas such as deserts. In addition to the skin, other structures that can be preserved over the millennia are nails, hair and bones and teeth.

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Natural mummy in the British Museum, London. Photo: Mireia Querol Rovira

Unlike fossils, which are millions years old, mummies do not usually exceed thousands of years, although there are fossils of dinosaurs with skin impressions or scales. If you want to know more about the processes of fossilization, we invite you to read Knowing fossils and their age. Ötzi is a sub-fossil because he is younger than 11,000 years old.

WHO WAS ÖTZI?

Ötzi, the Man of Similaun, the Man of Hauslabjoc or simply The Iceman, was discovered in the Ötz Valley (on the Austrian-Italian border of the Alps) by climbers in 1991 at 3,200 meters. Thanks to a storm in the Sahara, the dust reached the Alps and when it warmed with the sun, it melted the ice more than usual and uncovered Ötzi, who had been under the ice for more than 5,000 years. It was not until a later study that his real antiquity was discovered, since in situ seemed to be a dead climber.

Ötzi where it as discovered. Photo: Paul Hanny / South Tyrol Museum of Archaeology

Thanks to the technique Carbon 14, it was determined that Ötzi died around 3255 BC (Chalcolithic, Copper Age), which made it the oldest preserved mummy in the world. In addition to the body, more than 70 personal objects (weapons, clothing, tools…) were found, which gave more information about the life of this prehistoric man.

Ötzi’s close-up. Source

A MODERN HOMO SAPIENS

Throughout various posts we have talked about other species that preceded us , but Ötzi belonged to our species, Homo sapiens. The first Homo sapiens, who appeared in Africa 200,000 years ago, represented the evolutionary transition between H. heidelbergensis to the first modern humans. After more than 7 million years of evolution, H. sapiens are the only hominini survivors.

Ötzi’s reconstruction by artists Alfons and Adrie Kennis. Photo: Thilo Parg

H. sapiens migrated from Africa to the rest of the continents. If you want to know about how paleoparasitology helps us to follow the migratory routes of our ancestors, do not miss this post . When Ötzi was alive, the Neanderthals had already become extinct a few thousand years ago and their sapiens ancestors had been in Europe since about 45,000 years ago.

The difference between  H. sapiens and other species is a very rounded and large skull (1,000-1,400 cm 3 ) compared to the body, a flat and vertical face, small teeth a non-robust jaw, and the presence of chin, feature that does not have any of the preceding species.

Comparison of the skull of sapiens and neanderthalensis where wecan see the presence of the chin. Cleveland Museum of Natural History. Photo: Matt Celeskey

If we look at the skeleton, like other recent hominins, Ötzi and we are perfectly adapted to bipedism, with a distinctive light constitution. We have long lower limbs, with the femur tilted to the knee to keep the center of gravity under the body. The pelvis is narrow and short. The spine is curved to maintain balance and distribute weight efficiently while walking, with strong lumbar vertebrae. The arms are relatively short and the hands are agile and they have excellent prehensile precision, with long and thin phalanges compared to neanderthals.

Reconstruction of Ötzi, an H. sapiens like you. Photo: Thilo Parg

At cognitive level, what made us different from the rest of the hominin species is the symbolic thinking (representation of nature through symbols and abstract thinking), although the debate is still open since the Neanderthals had behaviors that could be considered symbolic (like decorating the body with jewelry or paintings). What is clear is that 40,000 years ago, the clearest evidence of modern behavior appeared in Europe, with the appearance of rock painting and sculpture. Technological innovation, agriculture and livestock are other of our distinctive features.

WHAT VALUABLE INFORMATION HAS REVEALED SCIENCE ABOUT ÖTZI?

Different techniques have been used to reveal information about the mummy and changing the different hypotheses over the years.

Scientist examining Ötzi. © South Tyrol Museum of Archaeology/EURAC/Samadelli/Staschitz

CARBON 14 AND DENTITION: AGE

Ötzi was about 46 years old when he died (life expectancy in the Copper Age was about 35 years). This data comes from the study of teeth, which are worn out, perhaps by eating grain throughout his life. The Carbon 14 test was carried out on its body and clothing: he is approximately 5,300 years old. It is estimated that he weighed about 45 kilos and he was 1.60 m tall.

COMPUTERIZED AXIAL TOMOGRAPHY (CT SCAN)

A  CT Scan in the body of Ötzi brought to light that he was suffering from various oral issues, such as caries (perhaps due to the consumption of bread and oats), periodontitis (pyorrhea) and worn  out teeth for using them as a tear tool. He also lost part of a molar and suffered a blow to an incisor.

Iceman’s hand. Photo: Robert Clark
Iceman’s feet. Photo: Robert Clark

He also suffered from arthritis, gallstones and he had a lump on one toe, broken nose and ribs that healed before death and had black lungs  because of inhaling CO2, maybe from bonfires. More than 60 tattoos (the oldest known) were found throughout his body, consisting of small lines, crosses and points. They were made with small cuts that were then rubbered with charcoal. They do not seem decorative: it is speculated that they were part of some treatment to improve the artirtis, since they indicate the points where he was in pain.

The mummy has 61 tattoos, most of them simple lines. Photo: Marco Samadelli and Gregor Staschitz /South Tyrol Museum of Archaeology

His system also had high levels of arsenic, probably because he worked with minerals and metals.

THE LAST DINNER

An analysis of the stomach revealed that he had eaten two hours before dying. He ate ibex (wild goat), cereals and unidentified plants. They found 30 different types of pollen, so he probably died in the spring. But they also found eggs of a parasite that cause Lyme disease, which mainly affects the vascular, nervous and skeletal system.

Stomach content of the Iceman. Photo: Robert Clark

X-RAYS: ACCIDENT OR MURDER?

First it was believed that Ötzi died due to crashing into a glacier. But radiographs revealed the presence of an arrowhead on his shoulder, so the researchers analyzed the body more closely and found several injuries in the hands, torso and a blow in the head, the cause of his death.

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Ötzi torso radiograph, arrow in red. Photo: Robert Clark

DNA ANALYSIS: HE SUFFERED DIVERSE DISEASES

Scientists did DNA tests in various blood samples, and they found up to 3 different types of blood. The blood of his flint knife is not from him: everything shows that he was involved in a fight with several people and was killed. His body was not found in a natural position, so two hypotheses are considered: either a partner tried to help him to extract the arrow or the enemies tried to recover it. In any case, they did not take away the advanced technology and Ötzi clothing. Why? The mystery is still open.

Ötzi’s clothing. Fuente
The Ötzi ax (foreground) has the copper blade, which indicates high status and it is the only one of Neolithic with the wooden handle intact. Source

In 2008 the complete genome of the Ice Man was published. He was lactose intolerant, his blood was type 0, he had brown eyes, he suffered from the heart and arteries and he is related to the current inhabitants of Corsica and Sardinia. In addition, out of 3,700 DNA samples were donated by Tyrol volunteers. 19 individuals share a genetic mutation with Ötzi.

NON-HUMAN DNA IN ÖTZI

The samples of non-human DNA are usually bacteria that live in our body. A biopsy on the hip brought to light the presence of DNA from a bacterium (Treponema denticola) involved in periodontal disease, which confirmed the results of the CT Scan. They also found remnants of the bacterium Clostridium and Helicobacter pylori  so Ötzi had a strong stomachache and diarrhea the day of his death. Besides, the study of Helicobacter from Ötzi has thrown new data on human migrations, the origin of European populations and the impact on our evolution.

More than 25 years studying Ötzi. Photo: Esame Colorimetrico / South Tyrol Museum of Archaeology

DO YOU WANT TO SEE ÖTZI?

This discovery is so important, that they dedicated a museum almost entirely for him: the South Tyrol Museum, in Bolzano. There are exposed the impressive clothes that he wore, made with animal skins such as bears and goats, his shoes, with double layer and stuffed with straw, his tools, weapons… even the first aid kit he was carrying. And he himself, of course, preserved at -6º. Maybe one day we will hear him “talking”: they are trying to reconstruct his tone of voice from the vocal cords.

Ötzi in his refrigerator room. Photo: South Tyrol Museum of Archaeology/Augustin Ochsenreiter

We still do not know who he was. Maybe a personality? A skilled hunter? A farmer or a stockman? A healer? We will probably never know. What is certain is that he could never imagine the attentions he would continue receiving 5,000 years after his death.

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

From traditional medicine to personalized medicine

From prehistory, where medicine started began with plants, minerals and parts of animals; until today, medicine has evolved very quickly. Much of the “fault” of his fact is due to genetics, which allows us to talk about personalized medicine. In the following article we discuss this.

THE EVOLUTION OF DISEASES

To talk about medicine, we have first to know diseases. We cannot think that all diseases are genetic, but there are diseases related to anatomical changes, fruit of our evolution.

Chimpanzees are the closest animal to us, humans, with which we share 99% of our genome. Despite this, humans have very particular phenotypic characteristics as the brain most develop, both in size and expansion of the cerebral cortex; hairless sweaty skin, bipedal posture and prolonged dependence on offspring, allowing the transmission of knowledge for longer; among other.

Possibly, the bipedal position was key to the early development of the divergence between the chimpanzee lineage and that of humans; and is also the reason for the appearance of some diseases related to anatomical factors. Among them are hernias, haemorrhoids, varices, disorders of the spine, such as herniated intervertebral discs; osteoarthritis in the knee joint, uterine prolapse and difficulties in childbirth.

The fact that the pelvis was remodelled (Figure 1) and narrower resulted in obstetric problems millions of years later, when the brain expanded. Consequently, the skull as well. The heads of the foetuses were longer and larger, making birth difficult. This explains why the deliveries of humans are longer and longer compared to those of chimpanzees and other animals.

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Figure 1. Comparison between human pelvis and chimpanzee pelvis in bipedal position (Source: Libros maravillosos – La especie elegida (capítulo 5))

The evolution towards modern life has behaved many changes in every way. In comparison to our hunter-gatherer ancestors (Figure 2), our diet has changed a lot and has nothing to do with what other primates eat. For the latter, the fruit represents most of the intake, but for us it is red meat. In addition, we are the only animals that continue to feed us milk after the lactation period.

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Figure 2. Picture of hunter-gatherer humans (Source: Río Verde en la historia

If we add to the sedentary lifestyle and the limited physical activity of modern humans, it can help explain the seriousness and frequency of some modern human diseases.

Lifestyle can also affect us. For example, myopia, which rate is higher in western individuals who read a lot or do activities of near vision, compared to individuals of Aboriginal’s towns.

Another clear example is the alteration in the female reproductive stage. Currently, women have children more and more later. This is also linked to a decrease in the duration of breastfeeding. These changes, which can be considered socially positive, have negative effects on the health of the reproductive organs. It has been shown that the combination of early menarche, limited or no breastfeeding and later menopause are the main risk factors for breast and ovarian cancer.

Humans increasingly live more years and we want the best quality of life. It is easy for more longevity to appear more diseases, by the deterioration of the organism and its cells.

THE EVOLUTION OF MEDICINE

The history of medicine is the history of the struggle of men against disease and since the beginning of this century, is also the history of human effort to maintain health.

We have acquired the scientific knowledge of medicine based on observation and experience, but it has not always been so. Our ancestors experienced sickness and the fear of death before a rational picture could be made of them, and the medicine of that time was immersed in a system of beliefs, myths and rites.

However, in the last years it has been born personalized genomics, which tells you your risk factors. This opens a door to personalized medicine, which adjusts treatments to patients depending on their genome (Figure 3). It uses information from a person’s genes and proteins to prevent, diagnose and treat a disease, all thanks to the sequencing of the human genome.

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Figure 3. Personalized medicine that treats people individually, according to their genome (Source: Indiana Institute of Personalized Medicine)

Molecular methods that make precision medicine possible include tests of gene variation, proteins, and new treatments targeting molecular mechanisms. With the results of these tests and treatments can determine the state of the disease, predict the future state of the disease, the response to the drug and treatment or even the role of the food we eat at certain times, which results of great help to the doctors to individualize the treatment of each patient.

To do this, we have within our reach the nutrigenetics and the nutrigenomics, that like the pharmacogenetics and the pharmacogenomics, they help the advance of a medicine is more and more directed. Therefore, these disciplines are today one of the pillars of personalized medicine since it involves treating each patient individually and tailor-made.

The evolution towards precision medicine is personalized, preventive, predictive and participatory. There is increasing access to information and the patient is more proactive, getting ahead of problems, preventing them or being prepared to deal with them efficiently.

REFERENCES

  • Varki, A. Nothing in medicine makes sense, except in the light of evolution. J Mol Med (2012) 90:481–494
  • Nesse, R. and Williams, C. Evolution and the origins of disease. Sci Am. (1998) 279(5):86-93
  • Mackenbach, J. The origins of human disease: a short story on “where diseases come from”. J Epidemiol Community Health. (2006) 60(1): 81–86
  • Main picture: Todos Somos Uno

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Parasites: signs on our way

The mysteries of human evolution, their development and their movementsthroughout history continue to create great interest and expectation. There are stillmany things to discover and understand about ancient societies, but thanks to thehelp of the science we are increasingly closer. Can parasites of the past shed light on those communities? We will discover it in thehands of the paleoparasitology.

WHAT IS PALEOPARASITOLOGY?

This is a branch of paleontology that study parasitological evidences in archaeological records, i.e.,studying parasites or remains of these found in ancient archaeological sites. The objective of these studies is to shed light on the origin and evolution of parasitic diseases that exist, as well as determine their phylogenetic relationships.  The study of ancient parasites allows us to know socio-cultural aspects of ancient societies as for example their diets, their level of hygiene, if human  were nomadic or sedentary, their migrations etc.

The materials studied by the paleoparasitology are generally fossilized tissueremains, mummies, fossils, coprolites (feces mummified) or sediments that have been able to be in contact with those who were the hosts of these parasites.

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Mummified human coprolites. (Image: M. Beltrame)

Find remains of a parasite in some of the samples is difficult, since the passage oftime destroys all evidence. Even so, usually eggs or Oocyst parasites found (since theyare forms of resistance that have managed to stay over the millennia).

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A egg of a louse (Pediculus humanus) found in a mummy of Brazil (12,000 years old). B. egg of Trichuris sp. found in Cape virgins, Argentina (6000 years old). (Image: Araujo).

In certain cases, manuscripts and drawings of ancient societies have providedinformation on the presence of certain parasites, such as for example ceramics thatwe observe below, where lesions that presents a person who suffers from cutaneous leishmaniasis is faithfully represented. In the next image we see a fossilized skull which presents very similar lesions.

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A. Modified image of a ceramic moche representing (red circle) lesions caused by leishmaniasis. (Image: Oscar Anton, Pinterest) B. mummified skull that shows very similar injuries. (Image: Karl J. Reinhard).

THE ARRIVAL TO AMERICA: HUMAN MIGRATIONS AND PARASITES

About 150,000 years ago appeared a new species of hominid in Africa: Homo sapiens. It began to expand in several waves to the rest of the continent, Europe, and Asia,carrying with them some parasites that had inherited from his ancestors (known as heirloom parasites). At the same time, they were acquiring along their journey a range of parasites due to interactions with other humans and animals (souvenir parasites).

Following the archaeological remains and parasitological  clues what ancient humans have left during their migrations, is possible to determine the routes followed by them. One of these routes was the arrival in the new world (America). We have always believed that the first inhabitants of the Americas came across the Beringia Strait (which joined at some point by ice Siberia with Alaska) about 13,000 years ago.

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Representation of the path followed by the first American settlers by the Beringia Strait Bridge. (Image: The siberian Times).
A few very interesting parasites that can be found in the American archaeological remains are Trichuris trichiura (nematode known as whipworm  and Ancylostoma duodenale (hookworm). These parasites need tropical or subtropical climatic conditions since the eggs are expelled with faeces and mature in the ground.
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A. At the top adult A. duodenale (Christopher Noble). At bottom we can view an A.duodenale egg (Image: Universidad Antioquia) B. Adult Trichuris trichiura (Invertebrate zoology Virtual collection) and at bottom its egg. (Microbiolgia blogspot).

How do they then survived the cold conditions of the regions of Siberia and Alaska in the last ice age? They could not. These parasites would have not survived those harsh climatic conditions, since to their maturation and transformation infective they need warm and moist environments. In addition, signs of infections not found by these parasites in Arctic populations, such as the Inuit.

So, researchers believe that migration across the Bering Strait was not the only one. Paleoparasitologic experts  Adauto Aráujo and Karl J. Reinhard proposed that there were two alternative routes. On the one hand proposed a costal route (along the coast, route b in the image) and a trans-pacific route (crossing the Pacific Ocean, route c). By these routes parasites had been able to survive and continue infecting humans.

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The arrival of man in America routes proposed by Aráujo and Reinhard based on paleoparasitologic remains. (Image: Aráujo, et al.)

Could they have been already there? This question has an easy answer. These intestinal parasites are specific from man, therefore, they need human hosts to complete their life cycles. If there were no humans in America, surely there would be this kind of parasites.

Another  parasitological fact that confirm this theory is the presence of Enterobius vermicularis, popularly known as pinworm. This parasite was linked for the first time to the ancestors of Homo sapiens and throughout history, has coevolved with them to give rise to several different subspecies. On the American continent have been found remains of two lineages of E.vermicularis, that could be because arrived hominids from different places with different parasites. In this case, the parasite if he could get through the Beringia Strait, since its life cycle does not depend so strongly on the environmental conditions.

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“Parasites suffer the same phenomena for evolution that humans and other organisms, as selection, extinction and colonization. For this reason, these specific parasites of man are excellent evidence that shed light on the movements of our ancestors”Adauto Aráujo, 2008.

REFERENCES

Check the evolution in your own body

42% of the US population and 11.5% of the Spanish people do not believe in evolution. However, there are different evidence that Darwin was right, some of them in your own body. Have you had your appendix or wisdom teeth removed? Find out in this post which vestigial organs you have inherited from your ancestors.

WHAT ARE VESTIGIAL STRUCTURES?

Vestigial structures (often called organs althouth they are not organs properly) are body parts that have been reduced or have lost its original function during the evolution of a species. They can be found in many animals, including humans.

Esqueleto de orca en el que se observan vestigios de las extremidades traseras. Foto: Patrick Gries
Orca skeleton in which vestiges of the hind limbs can be seen. This is a proof of its terrestrial origins. Photo: Patrick Gries

Vestigial structures were fully functional in the ancestors of these species (and in the homologous structures of other existing species), but currently its function is practically useless or it has changed. For example, the second pair of flying wings in some insects such as flies have lost their function and they have been reduced to balance organs (halteres). If you want to know more about the evolution of flight in insects click here.

Besides physical structures, vestigial features can also manifest itself in behavior or biochemistry processes.

WHY ARE THEY  EVIDENCE OF EVOLUTION?

Natural selection acts on species favoring features that increase their survival and eliminating the ones with no benefits, for example when changes appear in the habitat. Individuals with unfavorable characteristics will die or will breed less and that feature will be removed after some generations, while favorable traits will remain as their carriers can pass them to the next generation.

Sometimes there are features that are neither favorable nor unfavorable, so they continue appearing in the next generations. But all has a cost structure (energy, risk to become infected, develop tumors…), so selective pressure continues acting to eliminate something that is not conducive to the success of the species. This is the case of vestigial structures, which “take longer” disappear throughout evolution. Their existence reveal that in the past these structures had an important role in our ancestors.

FIND YOUR VESTIGIAL TRAITS

THE NICTITATING MEMBRANE

We talked about it in How animals see the world. The third eyelid is a transparent or translucent membrane that protects and moisten the eye without losing visibility. It is common in amphibians, reptiles and birds. Among primates, it is only functional in lemurs and lorises.

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Nictitating membrane or third eyelid of a masked lapwing (Vanellus miles). Photo: Toby Hudson

In humans the plica semilunaris is a remnant of the nictitating membrane. Obviously we can not move it but still has some lacrimal drainage function and helps on the eye movement (Dartt, 2006).

Plica semilunaris (pliegue semilunar). Foto: desconocido
Plica semilunaris. Photo: unknown

DARWIN’S TUBERCLE AND EAR MUSCLES

10% of the population has a thickening in the ear, a vestige of the common pointy ear in primates. This structure is called Darwin’s tubercle and has no function.

Variabilidad del Tubérculo de Darwin en la punta de la oreja (0= ausente). Puede presentarse en otras zonas del pabellón auditivo: ver publicación.
Variability of Darwin’s tubercle at the top of the ear (0 = absent).  Credit.
Comparación entre la oreja de un macaco y la nuestra. Fuente
Comparison between the ear of a yellow baboon (Papio cynocephalus) and ours. Credit

Also, primates (and other mammals) have mobile ears to lead the pinna toward the sound source: surely you have noticed it in your house dog or house cat. Humans (and chimps) no longer have that great mobility, although some people may move slightly pinna. It has been proven with electrodes these muscles are excited when we perceive a sound that comes from a particular direction (2002).

Auricular muscles responsible of movement of the pinna. Credit

The occipitofrontalis muscle has lost its function to prevent the head from falling, but participates in facial expression.

PALMARIS LONGUS MUSCLE

16% of Caucasians do not have this muscle on the wrist, neither 31% of nigerian people neither 4,6% of chinese people. It can even appear in one arm and not in the other or be double.

It is believed that this muscle actively participated in the arboreal locomotion of our ancestors, but currently has no function, because it does not provide more grip strength. This muscle is longer in completely arboreal primates (like lemurs) and shorter in land primates, like gorillas (reference).

And do you have it or not? Try it: join your thumb and pinky and raise your hand slightly.

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I have two palmaris longus in the left arm and one on the right. Photo: Mireia Querol

WISDOM TEETH

35% of people do not have wisdom teeth or third molar. In the rest, its appearance is usually painful and removal is necessary.

Yo no tengo el tercer molar. Foto: Mireia Querol Rovira
I don’t have the third molar. Photo: Mireia Querol Rovira

Our hominin ancestors had them, much bigger than ours. A recent research explains that when a tooth develops, emits signals that determine the size of the neighboring teeth. Reducing the mandible dentition and the other along evolution has resulted in reduced molars (and eventually the disappearance of the third).

Comparativa entre la dentición de un chimpancé, Australopithecus afarensis y Homo sapiens. Fuente
Comparison between the dentition of a chimpanzee, Australopithecus afarensis and Homo sapiens. Look at the reduction of the last three molars between afarensis and sapiens, Credit

THE TAILBONE

If you touch your spine till the end, you will reach the coccyx or tailbone. It is three to five fused vertebrae, vestige of the tail of our primate ancestors. In fact, when we were in the womb, in the early stages of embryo development a 10-12 tail vertebrae formation is observed.

Distintos estados en el desarrollo embrionmario humano y comparación con otras especies. Créditos en la imagen
Different stages in human embryonic development (1 to 8) and comparison with other species. Credits in the image.

Subsequently it is reabsorbed, but not in all cases: it has been reported 40 newborns with a tail.

Neonato nacido con cola. Una mutación ha evitado la inhibición del crecimiento de la cola durante la gestación. Fuente
Infant born with tail. A mutation has prevented the growth inhibition of the tail during pregnancy. Credit

Although we have no tail, currently these bones serve as anchors of some pelvic muscles.

mireia querol, mireia querol rovira, coxis, sacro, sacrum, tailbone, rabadilla
Tailbone position. Photo: Mireia Querol Rovira

SUPERNUMERARY NIPPLES (POLYTHELIA)

It is estimated that up to 5% of the world population has more than two nipples. These “extra” nipples can be presented in different ways so sometimes are confused with freckles or moles. They are located in the mammillary line (from the axilla to the groin), exactly in the same position as other mammals with more than two breasts (observe your house dog, for example). Usually the number of breasts corresponds to the average of offspring that has a mammal, so extra nipples would be a vestige from when our ancestors had more offspring per birth. Usual is 3 nipples, but has been documented a case of up to 8 nipples in a person.

Pezón suplementario debajo del principal. Fuente
Additional nipple below the main one. Credit

FIND YOUR VESTIGIAL REFLEXES AND BEHAVIOURS

PALMAR AND FOOT SOLE GRASP REFLEX

Surely you’ve experienced that if you bring anything into the hands of a baby, automatically he grabs it with such a force that would be able to hold his own weight. This reflex disappears at 3-4 months of age and is a remnant of our arboreal past and the way to grab the hair of the mother, as with the other current primates. Watch the next video in 1934 on a study of twins (minute 0:34):

On the feet there is also a reflex of trying to grab something when the foot of a baby is touched. It disappears at 9 months of age.

By the way, have you noticed how easily children climb on any handrails or higher zones in a playground?

GOOSEBUMPS

Cold, stress or intense emotion (eg, listening to some music) causes the piloerector muscle to raise the hair giving the skin the appearance of a plucked chicken. It is an involuntary reflex in which some hormones, like adrenaline (which is released in the mentioned situations) are involved. What utility had this to our ancestors and has in modern mammals?

  • Increasing the space between the skin and the external surface, so that hot air trapped between hair helps on maintaining temperature.
  • Looking bigger to scare off potential predators or competitors.
Chimpancé con el pelo erizado durante un display antes de un conflicto. Foto: Chimpanzee Sanctuary Northwest
Chimpanzee with hair bristling in a display before a conflict. Photo: Chimpanzee Sanctuary Northwest

Obviously we have lost hair in most parts of the body, so although we retain the reflex, it has no use to us or to keep warm or to ward off predators. The hair has been preserved abundantly in areas where protection is necessary or due to sexual selection (head, eyebrows, eyelashes, beard, pubis…), but in general, can also be considered a vestigial structure.

There are more vestigial structures but in this post we have focused on the most observable. In future posts we will discuss other internal structures, like the famous appendix or vomeronasal organ.

REFERENCES

Cooking also made us human

Cooking is a distinctive and unique feature of our species. After the success of Eating meat made us human, we continue delving into the nutrition of our ancestors as one of many factors that led us to Homo sapiens. We will analyze the contributions of our readers in the previous post on the importance of carbohydrates and the use of fire.

THE OPPORTUNIST OMNIVOROUS

In the previous post we learned that one factor that contributed to the fast growth of the brain was the increased intake of meat by H. habilis, that allowed them to save energy in digestion (Aiello, L. Wheeler, P, 1995). Another factor that allowed saving energy to dedicate to brain growth, since Lucywas bipedalism (Adrienne L. Zihlman and Debra R. Bolter, 2015).

One of the things that gave us evolutionary success is our ability to take advantage of almost any food, allowing our expansion around the globe. Current diets are varied and traditionally linked to the availability of the geographical area or time of year, which changed with the development of agriculture and livestock. Human groups studied in historical period without agriculture or livestock, hunt, fish and gather very different foods, but no groups exclusively carnivorous or exclusively vegetarian have been found (except Eskimos, who have traditionally fed on hunting and fishing because of the characteristics of their environment, frozen during almost all the year).

Hazdas going hunting The hazdas are a small African tribe of hunter-gatherers 1500 Photo:.. Andreas Lederer
Hazda people returning from hunting. The Hadza are a small African tribe of about 1500 hunter-gatherers. Photo: Andreas Lederer

The first tools, possibly used by Australopithecus but obvious since H. habilis, allowed our ancestors to get food that otherwise would have been impossible to get: drilling and tearing flesh, breaking the hard shells of nuts, and later crushing and grinding grain. Thus, the basis of our current supplies are hard cereal grains (e.g. rice, wheat) and the dried seeds of legumes (e.g. lentils), because our needing of protein intake is low, although meat is consumed in excess in the First World countries.

But before the advent of agriculture, our ancestors ate what they found: Neanderthals in hostile areas had to base the diet with meat and supplement it with vegetables when they were available, while in milder climate zones, like the Mediterranean , make use of aquatic resources as molluscs, turtles and fish. Furthermore, by its robust body and increased muscle they needed more protein intake.

Neanderthals collecting mussels in Gibraltar, one of the last settlements of this species. Photo: DK Discover

THE ORIGINS OF THE CUISINE

As we have seen, seeds are very nutritious because they are rich in carbohydrates (especially starch), but low in protein; in addition, legumes must be cooked to be assimilated. No other animal, except us and our ancestors, prepare food or cooks. Cooking is an unique human trait which opened an infinite number of possibilities in our nutrition.

CONTROL OF FIRE

The first traces of use of fire date back 1.6 million years ago in Africa, although the first reliable evidence is a hearth 0.79 million years old. The responsible: Homo erectus, but those who used fire continuously, especially for cooking, were a later species: Neanderthals.

 Homo erectus, AMNH, American Museun natural history, querol mireia, mireia querol rovira
Homo erectus, American Museum of Natural History. Photo: Mireia Querol Rovira

The advantages of controlling fire were numerous and very important, but in this post we will delve into the first one:

  • Cooking and food storage
  • Better hunting and scavenging: fire allowed them to obtain prey hunted by large carnivores or direct theirs to natural traps .
  • Protection from predators
  • Heat: increased survival when temperatures fell.
  • Light: they could extend its tasks when night had fallen, favouring social skills and later, the development of language. In addition, changing the circadian rhythm (24h internal clock) could have extended the reproductive period .
  • Access to new territories: burning areas of dense vegetation to take dead animals and make use of new areas and encouraging migration to cooler places.
  • Improved tools: wood tools made with fire are more durable.
  • Better hygiene: burning waste avoided infections.
  • Medicine: after H. erectus, the fire has been used as disinfectant and instrument sterilizer and for the preparation of remedies based on medicinal plants, as inhalation of vapors or preparing of  infusions.
    Homo erectus, Daynes, CosmoCaixa, mireia querol mireia querol rovira
    Homo erectus surprised by the strength of his spear warmed with fire. Figure by Elisabeth Daynès, CosmoCaixa. Photo: Mireia Querol Rovira

    ADVANTAGES OF COOKING FOOD

    • Variety in the diet: certain foodstuff is indigestible raw or difficult to chew (especially for individuals with dental problems). Stewed food is softer and easier to digest, allowing H. erectus expand their diet respect their ancestors, accessing food of higher nutritional value (Richard Wrangham, 2009). Cooking improves the palatability and increases the assimilable carbohydrate availability in tubers, vegetables… and therefore it gives them more energy value. According to Wrangham and other experts, raw foodism can be harmful to health, because our body is adapted to this “pre-digestion” in the stoves, which allows us to be the primate with the shorter digestive system in relation to the body.
    • Reduction of the teeth: tusks and teeth could have been reduced due to consumption of cooked food. A tooth that has to bite a boiled potato instead of a raw one can be 82% smaller. Less space were needed for chewing muscles and teeth in the skull, so the mouth and face became smaller. This free space can be dedicated to accommodate an increasingly large brain. H. erectus had a brain 42% larger than H. habilis.
    • Less energy consumption: energy and time dedicated to chew and digest cooked food is less, so the number of final calories obtained increases. This energy can be devoted to brain development rather than digesting food.

      comida neandertal, dieta neandertal, neanderthal, dietPossible Neanderthal diet. Photo: Kent Lacin LLC/The Food Passionates/Corbis.
    • Fewer diseases: raw food, especially meat, may contain potentially pathogenic or deadly bacteria and parasites. But from certain temperatures, many of these bacteria die, so eating cooked rather than raw, our ancestors increased their survival significantly.
    • Less poisoning: some plants, fungi and tubers are toxic if are consumed raw, like some edible mushrooms, sweet potato or potatoes with green areas.
    • Food preservation: by smoking meat, it could be kept in good condition for longer and take advantage of it in times of scarcity. In addition, cooked food lasts longer than raw food.

CONCLUSION

In short, cooking was another factor involved in the brain development and cognitive abilities of our ancestors, allowed energy savings to digest and chew food, decreased masticatory apparatus, allowed the young become earlier independent from their breast-feeding mothers (who could mate more often), improved immune system… Even improved social skills: left more free time so they could dedicate it to other tasks, such as cooperation to keep the fire, planning the collection or capture of food, distribution of food in the group acoording to range and health of individuals… intelligence enhanced cooking techniques, which in turn enhanced the intelligence, in an infinite wheel that still exists today.

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY

Eating meat made us human

Currently some of the world’s population can choose their diet: omnivorous, vegetarian, vegan, raw foodism, carnivorous, paleodiet… but what ate our ancestors?  Which diet is more suited to the one of our ancestors? Without going into polemics, we will discuss one of the crucial facts of the evolution from Australopitechus to Homo: the meat intake.

WHAT DID OUR RELATIVES EAT ?

One of the reasons given to follow a strict vegetarian or vegan diet is that as “we are apes”, they feed on fruits and plants, and moreover, a more “natural” diet  is achieved. Currently and traditionally the base of the world diet are the seeds of cereals (rice, wheat, corn, etc.) and legumes (beans, lentils…), which often require processing (flour, for example) and have nothing to do with their wild ancestors. Since agriculture and livestock was invented and we have selected the best varieties for human consumption, the label “natural” loses all meaning. Although transgenic food is now on everyone’s lips, we have been using the genetic modification for thousands of years.

In the top row, wild ancestors of lettuce, carrot and corn. Below, domestic varieties. Source

That we are apes and the natural thing is to eat vegetables, is also not entirely true. As primates have evolved in trees, hominids have a strict diet or mainly folivorous -leaves- and frugivorous -fruit- (gorillas, orangutans), while gibbons also complete their diet with invertebrates. Our closest relatives however (bonobos, chimpanzees) are omnivorous as they eat vegetables, fruits, invertebrates and even small mammals and other primates (althought in less proportion than vegetables).

Chimpanzee eating meat. Populations of chimpanzees have been described  hunting with spears made by themselves. Photo Cristina M.Gomes, Max Planck Institute.

No wonder then that our direct distant ancestors as Australopithecus Lucy, ate leaves, fruits, roots and tubers as the basis of their diet. Some species, in addition to vegetables, also fed on invertebrates and small vertebrates, similar to modern chimpanzees.

HERBIVOROUS AND CARNIVOROUS

Fruits have more sugars, although they are not very abundant in comparison with leaves and stems. But leaves have less nutritional value because they contain many fibers we can not absorb, such as cellulose. Legumes contain more protein than grains, but some essential amino acids and vitamins (such as B12) are absent or in a few proportion in vegetables and easily assimilable iron (hemo iron) is found only in food with animal origin.

In short, vegetables are harder to digest compared to animals, so mammalian herbivores have longer digestive systems, or compartmented stomachs, chew over long periods of time and some are ruminants, while carnivores have digestive systems with lower absorption surface and require little chewing of food.

Digestive systems of non-ruminant herbivores, ruminants, insectivores and carnivores. Unknown author

 

WHY OUR ANCESTORS STARTED EATING MORE MEAT?

2.6 million years ago, climate change made our planet cooler and drier. In Africa the savanna dominated much of the territory, so hominids had to deal with hard leaves, leaves covered with wax, hard or thorny stems, roots… these difficult to digest resources were utilised by Paranthropus, with large teeth and powerful musculature in the jaw to crush, although they had a similar brain to Australopithecus. They became extinct a million years ago.

Paranthropus boisei. Reconstruction by John Gurche, photo by Chip Clark.

But another group of hominins found a kind of resources that offered them more energy in smaller quantities, and were easier to chew: meat. Homo habilis was the first to eat meat at higher rates than the rest of relatives and also meats with more fat. It was an opportunist: they ate almost anything edible, instead, Paranthropus were specialists, so if their food was scarce, they had more possibilities to die.

BIG BRAINS …

While Australopithecus and Paranthropus had a cranial capacity of 400-500 cm 3, Homo habilis had up to 700 cm 3. This increased brain size allowed them greater versatility and ability to improvise to find food.

One thing that clearly differentiates us from other primates and animals is the large size of our brain. As you have noticed, H. habilis and is classified within our genus,  Homo, due to that great leap of brain size, among other things.

Skull comparison between Australopithecus, Homo habilis and Paranthropus. Credit: Peter S. Ungar et al, 2011.

But a large brain also has drawbacks: 25% of our body’s energy is consumed by the brain at rest, H. habilis brain consumed 15% and Australopithecus only 10%. In addition to quantity, this energy also has to have quality: some fatty acids for proper brain function only are found in some nuts, but especially in animal fat, easier to achieve if vegetables were scarce.

homo habilis, cosmocaixa, daynes, museu de la ciencia de barcelona
Homo habilis reconstruction by Elisabeth Daynès, Cosmocaixa (Barcelona). Photo by Mireia Querol

…SMALL INTESTINES …

The only way to dedicate more energy to brain function is to reduce the size of other high energy consumer organs (Aiello, L. Wheeler, P, 1995). Heart, kidney, liver, they are major consumers of energy, but vital, so the solution is to reduce the gut and that’s only possible with the change of an almost exclusively vegetarian diet (Australopithecus) to another of easier assimilation with more protein and animal fat (H. habilis).

Comparison between high energy consumer organs between humans and other primates. Image by J. Rodriguez

…AND TOOLS

A large brain also gave another advantage to H. habilis. Despite his appereance (small, no large fangs or claws) they could make use of a great variety of meat (first as scavengers and later as hunters) due to the use of tools. Australopithecus probably used some sort of simple tools, mostly wooden made, but we know for sure that early manufacture of stone tools (archaeological industry) belong to H. habilis. This allowed them to take advantage of the inside of the bone marrow of large prey killed by carnivores when all the flesh had been eaten by other animals. Currently only hyenas and bearded vultures can access this resource without tools. Besides, by not requiring such large teeth and jaws, the skull can accommodate a larger brain.

habilis, carronyer, carroñero, habilis, herramientas ,eines
H. habilis scavenging a rhino. Source; DK FindOut

CONCLUSION

In short, the increase of the brain of Homo was possible by changing diet, which allowed a shorter digestive tract and smaller masticatory apparatus. In turn, to achieve these more energy foods more intelligence is required, resulting in more complex behaviors such as the use of manufactured tools (Oldowan lithic technology, Mode 1).

Our digestive system is the result of millions of years of evolution as opportunistic omnivores. Some current strict diets (vegetarian or almost carnivorous) are in contradiction with this biological heritage and the abuse and access to all kinds of food carry us all kinds of allergies and food problems. The secret remains following a balanced and varied diet.

REFERENCES

Koko, the gorilla who can talk with her hands

The origin of language is one of the unknowns that creates more discussion among anthropologists. Are we the only animals with a language with grammar? Did our ancestors speak? Do animals communicate only by imitating simple sounds? This article will attempt to address these issues and introduce Koko, the gorilla who learned sign language.

CAN ANIMALS SPEAK ?

Clearly most living beings communicate in some way, either through visual, olfactory or chemical, acoustic signals… The clearest case we have close is barking, meowing… but also plants can communicate.

You have probably ever heard a parrot or parakeet say words, even the crows are great imitators. But it is just that, an imitation of few words. They are unable to make sentences or use the words they know to express new concepts. Or have a conversation. Sometimes scientists have educated baby apes as humans, in an attempt to teach them to speak. They never made it.

WHAT IS NECESSARY TO SPEAK ?

Given the depth of the subject, we can summarize that to talk is essential to have the necessary cognitive capabilities and a physical vocal apparatus that enables control of entry and exit of air in a certain way . Since some animals like whales, birds or apes have high cognitive abilities, why they do not start talking the same way as us? We begin to understand their way of communicating, so it is possible that some possess some sort of grammar, or a language such as dolphins or some birds. Or maybe we should clarify what is language. In this post we will focus on the case of primates, especially gorillas and chimpanzees.

VOCAL APPARATUS

The larynx contains the vocal cords. Notice the difference between a human and a chimpanzee:

Vocal apparatus of a chimpanzee and a human. Unknown author. Photo taken from UOC

Humans have the vocal cords in a lower postion, and we have a shortest oral and nasal cavity. To produce vocals clearly, the oral communication core, the larynx must be in a low position. That is why chimpanzees, cannot talk due to their physical limitations.

 

Model with the different positions of the vocal apparatus necessary to pronounce vocals. Photo by Mireia Querol, CosmoCaixa, Barcelona.

To investigate whether our ancestors could talk, studies focus mainly on the morphology of the hyoid bone, the position of the pharynx, the base of the skull and the brain impressions inside the skull. Recent research with Skull 5 of the Sima de los Huesos belonging to a Neanderthal, along with other studies of other fossils, suggests that 500,000 years ago they had a vocal apparatus like ours. If Neanderthals had the physical conditions did they speak?

BRAIN CAPACITY

Humans are the mammals with the largest brains relative to our bodies. The intelligence of a chimpanzee is compared to 4 years old child. If they can not speak for physical limitations, could they do it otherwise?

Cerebro humano señalando las áreas de Broca y Wernicke, responsables del lenguaje. Foto de dominio público tomada de NIH
Brain pointing out Broca’s and Wernicke’s areas, responsible for language. Homo habilis and possessed. Photo of public domain taken from NIH

According to a study published in Nature , the FOXP2 gene appears to be responsible for our ability to control of precises movement that allows speech. People with inactive copies of this gene, have severe speech and language problems. The FOXP2 gene is different in only two amino acids between chimps and humans, and apparently is responsible that neither they nor the rest of vertebrates can talk. This difference, this mutation is believed to have appeared 500,000 years ago. Svante Pääbo and his team discovered that this gene was already like ours in Neanderthals. If this is true, added to what we have seen in the previous section, we can almost ensure that Neanderthals could speak.

TEACHING TO TALK TO OTHER APES

Since they can not talk, scientists have taught apes to communicate with humans by lexigrams (drawings respresentan words) and sign language. Washoe was the first non-human ape to learn the American Sign Language (ASL). It was a chimpanzee, learned about 350 words and taught his son some Loulis. Other chimpanzees were capable of it, but the most fascinating is the discovery of this communication behavior of wild chimpanzees signs (obviously, chimpanzees own signs, not the ASL). The bonobo Kanzhi communicated with lexigrams, and Koko has become a famous gorilla thanks to her mastery of ASL.

KOKO THE GORILLA

Koko (short for Hanabiko,  in Japanese, “Fireworks”) is a western lowland gorilla. Gorillas are the largest apes and hominids nowadays, with up to 180 Kg weight in males.

Koko en 2010. Foto de Ron Cohn, Koko.org.
Koko in 2010. Photo by Ron Cohn, Koko.org.

 

After chimpanzees and bonobos, gorillas are the most genetically similar to humans (we share more than 98% DNA). There are two species of gorillas:

  • Western Gorilla (Gorilla gorilla) includes two subspecies, the western lowland gorilla (Gorilla gorilla gorilla) and the Cross River gorilla (Gorilla gorilla diehli). It is critically endangered according to IUCN .
  • Eastern Gorilla (Gorilla beringei): includes the mountain gorilla (Gorilla beringei beringei) and the eastern lowland gorilla (Gorilla beringei graueri). It is endangered according to IUCN .
Distribución gorila, bonobo, chimpance, orangutan, distribution, gorilla, chimpanzee,
Distribution of great apes. Map shared from Great Apes Survival Partnership

 

KOKO’S LEARNING

Koko was born in 1971 in the San Francisco Zoo, and currently lives in the Gorilla Foundation in Redwood City, California. Since she was 6 months old Dr. Francine (Penny) Patterson (then PhD student) and Dr. Ron Cohn taught her American Sign Language (ASL). Other gorillas that were attached to the project were Michael (in 1976) and Ndume (1991).

Penny teaching Koko (right) and Michael ASL. Photo taken from Koko.org
Penny teaching Koko (right) and Michael ASL. Photo taken from Koko.org

Since then, Koko has learned up to 1000 ASL signs and understands approximately 2,000 words in English. It is even capable of combining different signs to explain concepts if seh don’t know the word. Michael and Ndume also managed to communicate through signs: Ndume learned some from Koko, which could prove Koko’s case is not unique but gestural communication is intrinsic in gorillas.

In this video Penny asks what Koko would like to do with their spare time. She answers that she would like to have a baby and thanks Penny when she tells her that they are trying:

OTHER SKILLS OF KOKO

Koko, living in a humanized environment, performs acts by imitation, according to researchers, she has not been forced to do so. She look at books, movies, makes paintings, looks her in the mirror, take care of pets… even plays the flute. This is especially important because it is capable of puckering in the proper position and control breathing. It can also simulate cough, which requires control over the larynx. Contrary to what was thought, control over the airways and therefore on future capabilities of our ancestors speaking, could have appeared millions sooner than previously thought.

Koko video playing flutes and harmonica (Koko.org):

Another subject worthy of study is the artistic ability of Koko and Michael. If other apes have created tools and language, it is art what separates us from them and our ancestors? Since Koko can communicate with a common language to us and puts names to her creations, is this some symbolic capacity? The line between apes and other H. sapiens, and therefore also between H. sapiens and other Homo, is getting thinner.

Kokopainting a picture. Photo from Koko.org
Kokopainting a picture. Photo from Koko.org

 

PROJECT KOKO MILESTONES

Finally, we leave you with the most important milestones after 40 years of study with Koko:

    • Gorillas can learn ASL (1,000 signs) ant do it faster during childhood, and know how to modulate these signs to give them different emphasis
    • They understand spoken English (2000 words)
    • Koko is not a unique case, as Michael and Ndume testify
    • Inventive: they can expand language combining signs learned with other signs (eg, “bracelet finger” to express “ring”), or by adding own gestures .
    • Emotions: they express a variety of emotions, from the simplest to the most complex. It is known Koko reaction after the death of one of its kittens, Robin Williams, or a sad scene in film.
    • Hypothesis of empathy: the gorillas may have empathy, looking at how she treats persons or animals .
    • Use of grammatical language
    • Other ways to communicate: including creation of drawings, photographs, pointing to words, letters with phrases …
    • Self-identity: Koko is defined in front of a mirror as “fine animal / person gorilla”. Watch the video:

REFERENCES

MIREIA QUEROL ALL YOU NEED IS BIOLOGY