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Skip to 0 minutes and 15 secondsIn this chapter we are going to see the positions of humans in nature in the light of evolution. The idea is that to understand our positions in nature, we need to see where are we in relation to the living world. So, let's see where humans are, how humans have been considered historically and how we are seeing that now. The basic idea will come from the fact that today we are able to study our species and any other, both at the physiological, anatomical point of view, as classically has been done… Alongside with the analysis of our genome, and try to merge the knowledge into what are humans in nature within the evolutionary process.

Skip to 1 minute and 16 secondsSo we are going to see how humans have been classified, which are our closest relatives, and which is the position of humans in nature at the light of evolution, as we understand today. The zoological classification from Linné has been able to put humans in nature which was at the moment very important in recognizing them as animals, as mammals, as primates… But we are also within primates, we are in a group with monkeys, in a smaller group with Apes, and Hominids or as a family in which we are the only living species today.

Skip to 2 minutes and 14 secondsThe idea of this primate classification in which we have, by one side, the prosimians and then the simians; in the simians we have the new world monkeys, then we have the monkeys of the ancient world, and then we have the Apes. Apes are our closest relatives, and we have to distinguish very clearly by one side the group of Gibbons

Skip to 2 minutes and 50 secondsfrom the apes properly said; in which we have three main forming species: bonobo, chimp, gorilla, and orang and humans. This has been for many years and still needs the classification of humans; the position of humans in nature.

Skip to 3 minutes and 14 secondsThen the question is: “let's meet first our closest relatives to see to which extent we are very different or not”. Because we have to bear in mind, that to recognize the difference we need some objective measure that we do not have if we see, if we use just our feelings, our eyes, our perception to make the classifications; Because we are very used to see humans, and we are not so used to see other species, and we think that we are much more different that maybe what really we are. But let's meet them. So, the basic idea is that we have to recognize these species. First the chimpanzees. Chimpanzees are usually the best studied of all the Apes.

Skip to 4 minutes and 6 secondsThey live around 50 years. They are Africans. Bonobo, chimp and gorillas are Africans. They walk by knuckle walk; sometimes they do brachiation, but sometimes also they do bipedalism. They eat a variety of fruits, they also eat insects, and in some cases also meat. They have a highly developed visual sense, and they have a very highly developed social structure; very good in recognizing individuals, domination by males, very hierarchical groups of 20, -some 10/20 individuals- with very, very strong family groups. They are nomads in the forest, and they reuse their night nests the females move, and we are going to see that this is a very interesting point, because this is a way of avoiding inbreeding.

Skip to 5 minutes and 26 secondsAnd they are very territorial and aggressive; many times they use violence to resolve conflicts. By the other side, bonobos are the good guys of the group. They are also Africans, and they are restricted to one part in which chimpanzees are all around, but there is a river that is a very important boundary. And in this case bonobos also live very long times, some 50 years. They weight, some 30 kilos. Central Africa. Also knuckle-walking brachid, but bipedalism is more frequent in bonobos than in chimps. Also, they eat a variety of fruits, termites and meat. Very good visual sense, and they have also very interesting family groups.

Skip to 6 minutes and 32 secondsThey are much less aggressive than chimps, and they use a lot sex of all types to solve conflicts. In this case also females move from one population to the other. Next neighbor, gorillas. Gorillas are much bigger. The interesting, the distribution, there are two spots in Central Africa in which there is no relationship between the two, meaning that there are very, very clearly different groups of gorillas. They live some 40 years. They weight much more, a 100 kilograms. They spend most of the time on the floor, feeding mostly on roots and leaves. They are nomads, they move every day in groups of 12/20 animals, and they do new nests every night.

Skip to 7 minutes and 38 secondsThey are hierarchical and social and the groups are dominated by the silverbacks, the alpha males. And in general they are very, very peaceful. They are very well known by the work of people having been living there. The Asian, Southeast Asian ape; the orang or orangutan. In this case we have the distribution in two different islands, and for many people these are being considered two different species. And in general we could say that this men of the forest –this is the Indonesian meaning of orangutan- they live some 40 years, they weight between 40 and 80 kilograms, they have a very typical view with all these red hair. In the tropical forest, both Sumatra and Borneo.

Skip to 8 minutes and 39 secondsThey are frugivors, they eat quite a lot of vegetables. And in this case they use brachiation, and swing with the arms, they can go from one tree to the other. But they are too heavy to jump on a tree and spend lots of time on the floor, and also on knuckle-walking. They make nests, one new every night and they live lonely, the males; or in small groups with few females. But in general they are solitary, or of very, very small groups with no hierarchical structure than in other species. And last the lesser ape, the Gibbons and see amongst, in which we have several species. These are the smallest Apes, around ten kilograms and lives no more than 25 years. Frugivors.

Skip to 9 minutes and 51 secondsThey are acrobatic and brachiating, jumping from one tree to the other, they can also walk bipedal. They live in the tropical forests of Southeast Asia. There is no sexual dimorphism, which is interesting because this is going to be related to the hierarchical structure of the social groups; so when there is no social dimorphism, we are going to see later that this means that there is no hierarchy in the group. In this case, males and females can live in a stable group for many years and they defend the territory. It’s very nice as a model of stable pair of couple of individuals with no hierarchical structure.

Skip to 10 minutes and 48 secondsWe have now our neighbours, and if we want to see them together with humans, we have to see how we are going to put together, and relate one with the other. Traditionally in biology, it has been the taxonomy making groups. This is what has been done for many years and the idea is these different groups have been established through consensus of morphological, physiological characteristics. Later, in traditional zoology, they developed the systematics in the sense of looking to the diversification of the forms, past and present, and trying to fit, to be related to what could be the evolutionary process. But now, what we need to have is a view of the phylogenetics.

Skip to 11 minutes and 49 secondsMeaning that is not important which are the groups; but which is the process of evolution. And we are going to find that the closest is the one that we share more time in common in the evolutionary process. So, the phylogenetic is the study of evolutionary history and relationships among groups of organisms and species, populations… And these relationships are discovered through the phylogenetic inference methods to evaluate and the observable, heritable traits; in this case DNA. So, what we want to trace is the phylogenetic tree, is the understanding the tempo and mode of evolution, and to see exactly how it has been this process through time.

Skip to 12 minutes and 49 secondsBecause the process does not follow, does not reflect what the taxonomy has been doing through time. For example, if we go into the different families, genera and species, the classification does not reflect the evolutionary process. And we need to find the correct phylogeny. Here we have several of the phylogenies, possible phylogenies, and there have been lots of papers, lots of books, lots of discussion, on which is the correct phylogeny?

Skip to 13 minutes and 32 secondsHere the question is: bonobos, chimps, gorillas, orangs, humans… Which is the fine relationship among them? Which is the correct phylogeny? And we have to recognize that the classical view of morphology has not been able to solve it properly, because doesn't have a way in putting, in measuring, the affinities to infer common ancestry.

Skip to 14 minutes and 8 secondsSo, we reach the question: Which is the living being evolutionarily closest to humans? Which is the phylogeny?

Humans in nature

We are going to trace the tree of evolution, which includes our relatives: the bonobo, chimp, gorilla, orangutan and humans. We’ll also define the similarities in the sense of evolution. And we’ll establish the molecular clock. How important is nature for humans?

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Why Biology Matters: Basic Concepts

Pompeu Fabra University Barcelona