Arxiu d'etiquetes: homínids

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

Qui són els homínids?

L’article d’avui està dedicat als primats. Coneixerem algunes de les seves principals característiques, com es classifiquen les espècies actuals i descobrirem qui són els homínids i els hominins.

CARACTERÍSTIQUES GENERALS DELS PRIMATS

Els primats són un ordre de mamífers placentaris que va aparèixer fa quasi 65 milions d’anys a la selva plujosa tropical. Actualment existeixen més de 400 espècies vives, la majoria de vida arborícola. Atès que no hi ha una tret únic que els defineixi, són difícils de classificar, així doncs s’ha de considerar tot un conjunt de característiques, de les qual destaquen:

  • Sistema visual complex: amb els ulls situats de manera frontal, la seva visió és estereoscòpica, cosa que els permet percebre la distància i profunditat amb gran precisió. La majoria d’espècies veuen en color.
  • Alta mobilitat de l’espatlla: facilita el moviment del braç en totes direccions.
  • Mans i peus: tenen cinc dits i el polze oposable (almenys a les mans) cosa que els permet agafar i manipular objectes amb precisió. Encara que alguns tenen urpes, la majoria tenen ungles planes i tots (excepte alguns orangutans) tenen una ungla plana al dit gros del peu.
  • Tors i cua: diversos primats reposen i es desplacen amb el tors erecte. Excepte els simis, posseeixen una cua en alguns casos prènsil, que utilitzen com una cinquena extremitat.
  • Mida del cervell: a més d’algunes espècies de balenes dentades, els primats superiors tenen, en relació al cos, el cervell més gran de tots els mamífers.
  • Organització social: només orangutans, alguns lèmurs i gàlags són solitaris, la resta de primats s’organitzen en grups socials complexos.

    Goril·la menjant (Gorilla sp.) on s'aprecien algunes de les característiques descrites. (Foto: pixabay.com)
    Goril·la menjant (Gorilla sp.) on s’aprecien algunes de les característiques descrites. Foto: pixabay.com

CLASSIFICACIÓ

Fins fa poc les relacions entre diferents grups de primats no han estat clares, així que habitualment alguns termes duen a confusió o s’utilitzen de manera indistinta de manera popular (micos, simis…). La cladística moderna classifica els primats en dos subordres, els Haplorins (“primats de nas sec”) i els Estrepsirins (“primats de nas moll”). Una possible classificació seria la següent:

Tradicionalment els primats es classifiquen en tres grups: prosimis, mones o micos i simis.

PROSIMIS

Els prosimis són el grup més antic de primats. Es distribueixen pel sud-est asiàtic i illes marginals d’Àfrica. Comprenen els lèmurs, loris, gàlags, indris, l’ai-ai i els tarsers. Tenen en comú les següents característiques:

  • Urpes enlloc d’ungles (tenen almenys una ungla).
  • Musells llargs amb nas humit. Són els primats amb major sentit de l’olfacte.
  • Major orientació lateral dels ulls que la resta de primats. Aquests són grans i tenen bona visió nocturna.
  • Pavellons auditius mòbils.
  • Menor proporció cerebral dels primats.

    Ai-ai (Daubentonia madagascariensis). (Foto: Frans Lanting)
    Ai-ai (Daubentonia madagascariensis). Foto: Frans Lanting

    Tarser de Filipines (Foto: Kok Leng Yeo)
    Tarser de Filipines (Carlito syrichta). Foto: Kok Leng Yeo

 MONES DEL NOU I VELL MÓN

Les mones del Nou Món es distribueixen per Amèrica Central i del Sud. Tenen la cua llarga, freqüentment prènsil. El musell és pla i les narius laterals. Són totalment arborícoles. Els representants més coneguts són els titís, la mona aranya, els caputxins, i els sakís.

Sakí cariblanco macho (Pithecia pithecia). (Foto: Charles Miller).
Sakí de cara blanca mascle (Pithecia pithecia). Foto: Charles Miller

Les mones del Vell Món es distribueixen per Àfrica i Àsia. Solen tenir una mida superior a les del Nou Món. Les narius estan orientades cap avall o cap endavant i comprenen una gran diversitat d’espècies, com els macacs, papions, mandrils, mangabeis, drils, còlobs, nassuts, langurs…

Langur dorado (Trachypithecus geei). (Foto: Wikimedia).
Langur daurat (Trachypithecus geei). Foto: Wikimedia

SIMIS

Els simis es divideixen en dues famílies: els hilobàtids (gibons i siamangs) i els homínids (orangutans, goril·les, ximpanzés i humans). Es distribueixen per Àfrica occidental i central i pel sud i sud-est asiàtic, amb excepció dels humans, que ens distribuïm per tot el planeta i hàbitats.  Els simis tenim la cara plana, amb les narius cap avall i una anatomia que facilita la postura erecta i la manipulació precisa de materials, que inclou l’ús i creació d’eines en algunes espècies.

Ximpanzè (Pan paniscus). Pierre Fidenci
Bonobo (Pan paniscus). Foto: Pierre Fidenci

En conclusió, els homínids som els éssers humans (Homo sapiens) conjuntament amb orangutans (dues especies: Pongo pymaeus i Pongo abelii), ximpanzès (Pan troglodytes), bonobos (Pan paniscus) i goril·les (dues especies: Gorilla gorilla i Gorilla beringei), ja que tots pertanyem a la família Hominidae. El terme homínid també es refereix a totes les espècies fòssils d’aquest família, i per tant, als nostres avantpassats, que tractarem en futurs articles sobre evolució humana. Malgrat això, actualment per referir-nos exclusivament a les espècies de la nostra branca evolutiva (inclòs H. sapiens) s’utilitza el terme hominins, que fa referència a una tribu (Hominini) de la família Hominidae.

REFERÈNCIES

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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.

Gorila comiendo (Gorilla sp.) donde se aprecian algunas de las características descritas (Foto: pixabay.com)
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:

Taxonomia primates english
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, galagosindris, 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). (Foto: Frans Lanting)
Aye-aye (Daubentonia madagascariensis). Photo: Frans Lanting

 

Tarser de Filipines (Foto: Kok Leng Yeo)
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.

Sakí cariblanco macho (Pithecia pithecia). (Foto: Charles Miller).
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

Langur dorado (Trachypithecus geei). (Foto: Wikimedia).
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). (Foto: Pierre Fidenci)
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 paniscusand 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

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