Monday, November 24, 2008

Primate evolutionary tree: a case of eight stage evolution leading to humans?

I have been looking at primate evolution and taxonomic tress for quite some time and am aware that different scholars parse the same tree in different ways, specifically people try to avoid being anthropocentric. I , on the other hand , will focus exclusively on the primate tree as it relates to humans and try to to show that it might be a living proof of the eight stage theory of evolution/ development.

First let me show you a popular way of portraying the primate tree from Philadelphia Inquirer's Going Ape website.

Now, let me show you an alternative classification (just slightly different from this, but based on cladistics) . It is hard to see the figure (I've lost the original full -kleght versions), but the idea is that the first level branching happens at the level of suborder, then infraorder, then family etc within the order of primates.

Here is a similar diagram from the The Third Chimpanzee by Jared Diamond.

It is instructive to note that here barnching within primate tree is as follows:

  1. Suborder branching: Prosimians: I hypothesize that prosimian evolution be driven by first adaptive problem that of hiding from / avoiding predators. (lemurs etc)
  2. Infraorder branching: Platyrrhine (flatnosed) or New World Monkeys: I hypothesize that these would be most adventurous of all and would be focussed on finding food and resources, having mastered the predation problem. Maybe the main factor here would be their range size etc. This family is as opposed to Catarrhine (down-nosed) or Old World primate to which humans belong.
  3. Superfamily branching: Cercopithecoidea: Old World Monkeys. Lets say we focus on old world monkeys here. The hypothesis is that they would be specialized for forming alliances and territorial hierarchical behaviors. This superfmaily is as opposed to hominoidea superfamily.
  4. Family branching: Hylobatidae or Gibbons: the hypothesis is that Gibbon evolution may be driven by parental investment conflicts. this family is as opposed to Hominidae to which humans belong.
  5.  Subfamily branching: Ponginae or Orangutans :  Orangutan evolution may be driven by kin selection concerns.
  6. Tribe branching: Panini or gorillas: Gorilla evolution may be driven by theory of mind considerations. Maybe the driving force behind gorilla evolution is reading others mind and we would find good evidence for the same in gorillas. 
  7. Species branching: pan of chimpanzees and bonobos and humans: may be driven by communication or language concerns. Of course language or communication in Humans is phenomenal; but may be of equal importance for the other two also.
  8.   This species may be a branching of humans later on along sexual selection lines or assortative mating considerations along the lines of Elois and Morlocks.
I am not a primatologists and the above appears too simplistic and fishy to me; but is there evidence for any of the  hypothesis presented above; if so do let me know! Meanwhile I will be on the lookout for any confirmatory evidence!!

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