What Does the Primate Family Tree Look Like?
This figure is adapted from The Demonic Male (Mariner Books, 1997) past Richard Wrangham. Mariner Books hide caption
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Mariner Books
This figure is adjusted from The Demonic Male (Mariner Books, 1997) by Richard Wrangham.
Mariner Books
As anticipated concluding week, I'yard hither at the Dandy Ape Trust in Iowa, where I've spent a fantastic afternoon with Sue-Savage Rumbaugh and seven bonobos. Since I'll also be here tomorrow, I'll web log about the total experience adjacent week. This week I'll keep the smashing-ape theme by walking through the above image — Our Family Tree — and reflecting on some of its implications.
Charles Darwin is best known for his recognition that Variation and Natural Choice serve as the drumbeat of biological development. Simply fully equally important, to my mind, was his joint of the concept of Common Ancestry: all modern beings share beginnings, via countless convergences, with an original cellular brute (as expanded here). Darwin'due south one published cartoon offers a spindly sketch of this key insight, a sketch that looks for all the world like gimmicky understandings of evolutionary relationships, like Our Family Tree.
An important spin on this idea, developed by Richard Dawkins in his marvelous book The Antecedent's Tale, is the concept of the Most Contempo Common Antecedent or MRCA. I pull my students into the MRCA concept with this image documenting that persons named Samuel Hinkley and Sarah Soole, of Barnstable MA in the mid-17thursday century, were the MRCAs of Barack Obama and George Bush. Obama and Bush for certain share common ancestry with fish and worms and amoebae, but their well-nigh recent common ancestors are Hinkley and Soole.
The MRCA of humans, chimpanzees, and bonobos is indicated by the dashed circle in Our Family unit Tree. Circa 6 one thousand thousand years ago — an eyeblink in evolutionary time — in that location occurred a bifurcation, with the Human lineage moving along one path to present times and the Pan lineage moving along a second. More recently, some one to two million years ago, a second bifurcation occurred, yielding Pan troglodytes (common chimpanzee) and Pan paniscus (bonobo).
So here'south the six-million-dollar question: What was the human being-chimp-bonobo MRCA similar? A great ape for sure. But what well-nigh beliefs? Was it Human-like? Pan-like? And what practise we mean by such distinctions?
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Well, the short answer is that nobody knows the reply. But there are some interesting ways to frame speculation forth these lines.
If we start with modernistic chimps and bonobos, they manifest some striking behavioral differences. ane) Chimp societies are characterized by potent male dominance hierarchies, whereas bonobo societies have strong female authority hierarchies. 2) Chimp males accept been documented to engage in warfare with neighboring troops and impale troop members, whereas such behavior has not been observed in bonobos. 3) Chimp males are known to engage in infanticide, again a behavior unreported in bonobos. four) Chimps engage in sex only when females are in estrus ("heat"), at which times males brand smashing efforts to monopolize females and hence guarantee paternity. By dissimilarity, bonobos engage in sexual practice often (x times per twenty-four hours has been reported) and throughout the oestrus cycle, and seem quite disinterested in keeping track of paternity. 5) Homosexual sexual practice has not been observed with chimps, whereas it occurs frequently between female person and often between male bonobos.
If we now take this list and utilise it to humans, nosotros come up to an intriguing realization: depending on the civilization and, indeed, on the individual, we tin can recognize both patterns. We find dominant males and dominant females; we find warlike and peaceable cultures and persons; we find restricted and laissez-faire sexual practices; and nosotros find heterosexual, bisexual, and homosexual preferences.
Putting all this together, then, a case can be made that 1) the MRCA to the 3 lineages was endowed with both chimp-similar and bonobo-like tendencies; 2) in the Pan radiation, these bifurcated into 2 distinctive sets of behaviors in troglodtyes and paniscus; and three) in the Homo radiations, the "mixed bag" persisted.
Speculation? For sure. Only the next time y'all're at a human gathering and detect yourself bored, you might amuse yourself by engaging in a P. troglodytes vs. P. paniscus taxonomic exercise.
The humans at the gathering will, of course, be using syntactical symbolic language nonstop. This is our defining trait. The project at the Great Ape Trust is to ascertain the extent to which bonobos can learn elements of that trait when they are raised in a Pan/Human civilization. More side by side week!
Source: https://www.npr.org/sections/13.7/2010/12/09/131931215/our-family-tree-chimps-bonobos-and-our-commonality
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