Peter B. Gray Ph.D.

The Evolving Father

Great, Great, Great, Great…Ape Men

Reflections on great apes, hominins and wise old men.

Posted Dec 07, 2015

wikimedia.org
Source: wikimedia.org

At the Jardin des Plantes in Paris, there is a statue of the biologist Jean-Baptise Lamarck and his daughter. Well ahead of Charles Darwin’s formulation of evolution by natural selection, Lamarck embraced the idea of evolution, even if his view of the processes guiding it differed. Lamarck advanced the idea of inheritance of acquired characteristics. Traits are maintained by use and disuse, helping account for the apparent fit between a trait and an environment. While Lamarck is frequently chided in contemporary evolutionary biological discussions (a man’s musculature, which is developed in the gym isn’t passed on to his son, nor is a circumcised penis transmitted across generations), more recent advances in epigenetic and cultural transmission partly vindicate these concepts. As a phrase translated on Lamarck’s statue notes, “History will admire and avenge you, my father.”

In the present meditation on our distant ape forefathers and the processes that got us from them to us, it seems appropriate to begin with Lamarck.

A new book, David Begun’s (2015) The Real Planet of the Apes, allows us to mentally travel back to an era of great apes. Try to imagine what your very distant male ancestors were like 15 million years ago, 10 million years ago, at times before giving rise to the lineages that would split some 7 or so million years ago into those leading to modern humans on one branch and chimpanzees/bonobos on another. What do you see? In a current overview of fossil and ecological evidence, Begun portrays forests inhabited by relatively sparse but speciose (many species, but relatively small populations of each) great apes. With a deeper ancestry in Africa, Begun hypothesizes that the common ancestor of great apes evolved in Europe before splitting off into different lineages, including that returning to Africa to give rise to humans, among others. These were largely vegetarian, tree-hanging fighters, judging by the dental and other fossil evidence. “Humans share a very large number of features with great apes…which only make sense if we evolved from a common ancestor that spent most of its time in the trees, sitting on or hanging from branches, with a backbone positioned vertically. Our mobile shoulders and wrists, our hingelike elbows, our barrel chests, our shorter lumbar spines, and our orthograde posture are all shared with great apes.” (p. 211).

It’s hard to say much more specific about our great ape forefathers. However, as we time travel closer to the present, some features of our male ancestors becomes less hazy. This past year, several magnificent finds helped inform our understanding of hominin evolution. Hominins are humans and extinct relatives since splitting off from a common ancestor with chimpanzees/bonobos. In spring 2015, my UNLV colleague Brian Villmoare and collaborators published on a new find from Ethiopia dated to 2.8 million years ago. This partial jaw and teeth exhibited characteristics assigning it to our genus—Homo—thus pushing back by 500,000 years the earliest fossil evidence of Homo. In summer 2015, Lee Berger and colleagues published on remarkable finds from the “Rising Star” cave in South Africa. While lacking dates, the remarkable amount of skeletal material suggests a hominin containing both traits of Australopithecus and Homo. This hominin exhibited a small brain, short stature, and relatively longer legs. Furthermore, these findings suggest that members of our genus were finally giving up the trees in favor of committed bipedal ways on the ground. That commitment to the ground (after all those millions of years of life in the trees) allowed hands to be reshaped (shorter and straighter fingers) and used to do other things like make and use a wider variety of tools.

How did male hominins behave? Did they have caring fathers? What roles might fathers have held? A combination of fossil, archaeological, and hunter-gatherer data help address these kinds of questions about ancestral fathers. These early male Homo males may have formed long-term slightly polygynous mating bonds, engaged in protective defense of a mate and offspring, but done little in the way of provisioning, direct child care or sharing moral tales. The evidence suggests that human fatherhood is a mosaic of traits that evolved in different times and contexts.

This brings us back to Lamarck. While chimpanzees make plant tools and orangutans in captivity can play with IPads, humans stand apart from our ape cousins in our capacity for cumulative cultural evolution. We can learn from our elders, stand on the shoulders of giants, contemplate the ideas of a Lamarck or Darwin. We can read books on cultural evolution—take Joe Henrich’s (2015) new book, “The Secret of Our Success” (the secret is our capacity for culture). The processes by which we do this are Lamarckian at their core—they are acquired from elders as well as others. Indeed, in an old book on aging, Leo Simmons (1970) observes: “Most primitive societies have insured some respect for the aged…[U]nder close analysis, respect for old age has, as a rule, been accorded to persons on the basis of some particular asset which they possessed. They might be respected for their extensive knowledge, seasoned experience, expert skill, power to work magic, exercise of priestly functions, control of property rights, or manipulation of family prerogatives.” (pp. 50-51)

Imagine some of our Homo forebears. They have the hands and minds to employ new kinds of tools. Many of these tools are used to process foods, taking some wear and tear off their teeth, maybe allowing a few to live longer lives than otherwise possible. Perhaps living in larger groups than ancestral great apes, maybe these ancestors benefit from shared ideas and items, helping buffer mortality threats (a few more minds help remember where to find water or other key resources during duress). It becomes more possible to live longer lives; at ages when gorilla, orangutan, chimpanzee or even extinct ape ancestors of millions of years past would have all been dead, a fraction of older males (and females) remains. Those males have stories to tell. They have insights to share. They garner respect. They pass on ideas, as did Lamarck, that are part of what has enabled humans to be distinguished from our great ape kin.

References

Begun, D. R. (2015). The Real Planet of the Apes: A New Story of Human Origins. Princeton: Princeton University Press.

Berger, L. R., Hawks, J., de Ruiter, D. J., Churchill, S. E. et al. (2015). Homo naledi, a new species of the genus Homo from the Dinaledi Chamber, South Africa. eLIFE, 4, e09569.

Henrich, J. (2015). The Secret of our Success: How Culture if Driving Human Evolution, Domesticating Our Species, and Making Us Smarter. Princeton: Princeton University Press.

Simmons, L. W. (1970). The Role of the Aged in Primitive Society. New Have: Archon.

Villmoare, B. Kimbel, W. H., Seyoum, C., Campisano, C. J., DiMaggio, E. N., Rowan, J., Braun, D. R.,  Ramon Arrowsmith, J., and Reed, K. E. (2015). Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia. Science, 347, 1352-1355.