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 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.

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

• Roberts A (2002).  Evolución: historia de la humanidad. Akal, UK.
• Mateos A, Rodríguez J (2010). La dieta que nos hizo humanos. CENIEH, Burgos.
• Arsuaga J L, Martínez I (2006). La especie elegida. La larga marcha de la evolución humana. Booket divulgación.
• Potts, Richard. Sloan, Christopher (2010). What does it mean to be Human? Ed. National Geographic Society.
• Vegetarianismo – Aspectos nutricionales a tener en cuenta cuando te planteas ser vegetariano
• Paleodieta: hábitos prehistóricos para otra dieta milagro (OCU)

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?

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 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 .

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

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

 

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

• Human development (2002). Delval, J. XXI Century Editors Spain
  
• Koko.org . The Gorilla Foundation
• Sobre els Orígens the llenguatge (UOC)
• Instituto Max Planck. Hace medio millón de años una mutación nos ayudó a hablar y aprender
• Los monos ya saben hablar
• La ampliación del espacio cognitivo en el eje filogenético
• Áreas Broca’s and Wernicke (EduCaixa)
• Los simios y sus increíbles capacidades
• Gorillas (Great Apes Survival Partnership)
• Cover image: frame of the documentary “Koko, A -1978 talking gorilla.” Photo taken from mubi .

Who are the hominids?

Today’s article is dedicated to primates. We will talk about some of its key features, the classification of the living species and we will discover who the hominids and hominans are.

GENERAL CHARACTERISTICS OF PRIMATES

Primates are an order of placental mammals that appeared about 65 million years ago in the tropical rainforest. There are currently over 400 living species, most of them arboreal. Since there are no single trait that defines them, they are difficult to classify; so we have to consider a set of features, which are:

• Complex visual system: with frontally placed eyes, their vision is stereoscopic, allowing them to perceive the distance and depth with great accuracy. Most species can see in color.
• High mobility of the shoulder: allows an easy arm movement in all directions. Hands and feet have five fingers and opposable thumb (at least in hands) allowing them to grasp and manipulate objects with precision. Although some have claws, most have flat nails and all (except some orangutans) have a flat nail on the big toe.
• Torso and tail: several primates rest and move with an erect torso. Except apes, in some cases they have a prehensile tail, and can use it as a fifth limb.
• Brain size: besides some species of toothed whales, some primates have, in relation to the body, the largest brain of all mammals.
• Social organization: only orangutans, some lemurs and galagos are solitary, other primates are organized in complex social groups.

Gorilla eating (Gorilla sp.) where whe can see some of the characteristics. Photo: pixabay.com

 

CLASSIFICATION

The relationships among the different groups of primates were not clearly understood until relatively recently, so the commonly used terms are somewhat confused (mokeys, apes…). Modern cladistic classifies primates in two suborders, Haplorrhini (“dry-nosed primates”) and Strepsirhini (“wet-nosed primates“). A possible classification would be:

Primates taxonomy. Clic to enlarge. Created by Mireia Querol based in an image taken of humanorigins.si.edu.

Traditionally primates are classified into three groups: prosimians, monkeys and apes.

PROSIMIANS

Prosimians are the oldest primate group. They are distributed throughout Southeast Asia and Africa marginal islands. Prosimians include lemurs, lorises, galagos, indris, the aye-aye and tarsiers. They share the following characteristics:

• Claws instead of nails (they have at least a fingernail)
• Long snout with wet nose. They have the best sense of smell among primates
• More lateral orientation of the eyes than other primates. These are big and have good nocturnal vision
• Mobile pinna
• Minor brain proportion than other primates

Aye-aye (Daubentonia madagascariensis). Photo: Frans Lanting

 

Philippines tarsier (Carlito syrichta). (Photo: Kok Leng Yeo)

OLD AND NEW WORLD MONKEYS

The New World monkeys are distributed throughout Central and South America. They have a long, often prehensile tail. The muzzle is flat and the nostrils are situated in the side. They are completely arboreal. The best known representatives are marmosets, spider monkeys, capuchins, and sakis.

Male of White-faced saki (Pithecia pithecia). Photo: Charles Miller

 

The Old World monkeys are distributed throughout Africa and Asia. Usually they are bigger than New World monkeys. The nostrils are directed downward or forward. The Old World monkeys cover a wide range of species, such as macaques, baboons, mandrills, mangabeis, drills, colobus, proboscis monkeys, langurs …

Gee’s golden langur (Trachypithecus geei). Photo: Wikimedia

 

APES

Apes are divided into two families: Hylobatidae (gibbons and siamangs) and Hominidae (orangutans, gorillas, chimpanzees and humans). They are distributed throughout West and Central Africa and South and Southeast Asia, except humans: we are distributed all over the planet and habitats. Apes have a flat face, with the nostrils downwards and an anatomy that facilitates upright posture and materials handling, including the creation and use of tools in some species.

Bonobo (Pan paniscus). Photo: Pierre Fidenci

In conclusion, hominids are human beings (Homo sapiens) together with orangutans (two species: Pongo pymaeus and Pongo abelii), chimpanzees (Pan troglodytes), bonobos (Pan paniscus) and gorillas (two species: Gorilla gorilla y Gorilla beringei), because we all belong to the family Hominidae. The term also refers to all fossil species of this family, and therefore our ancestors, that we will discuss in future articles on human evolution. However, to refer exclusively to our evolutionary branch (including H. sapiens) the used term is hominans or hominas, which refers to a tribe (Hominini) of the Hominidae family.

REFERENCES

• Clutton-Brock, Juliet et al.  2002. Animal. Pearson Educación
• Roberts, Alice. 2002. Akal. Evolución: historia de la humanidad.
• The Enciclopedy of Life
• The Smithsonian Institution’s Human Origins Program
• Cover photo by Miquel Llorente

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