2. Some of Our Oldest Relatives

Like it or not, the chimpanzee is our closest living relative, responsible for 94% of our DNA. It belongs to the genus Pan that has only two members: Chimpanzee (Pan troglodytes) and Bonobo (Pan paniscus). The genus Pan diverged from the human branch 4 to 6 million years ago. Both genus, Pan and Homo have co-existed since the Middle Pleistocene era and have remained startlingly similar in behavior.

The two species of genus Pan have some interesting differences and it seems to me that both personalities can be seen in the human family. The common chimpanzee is an omnivore with sophisticated group hunting strategies overseen by an alpha male. It has a complex society complete with a hierarchy, politics, and all the social ills evident in human behavior. Its relative, the bonobo, is remarkably different. It is a frugivore (a fruit eater), is non-violent and egalitarian by nature. The bonobo has a complex matristic society; it is sexually receptive and uses sex to resolve and prevent conflict.

Chimpanzees are status conscious creatures capable of manipulation and deception. They have demonstrated the capacity to plan for the future. The chimpanzee alpha male is determined by how manipulative and politically influential he is. He attains dominance by winning over allies, often with threatening behavior and intimidation. Females have a hierarchy too and the alpha female, so to speak, is often a descendant of a high ranking mother. Females also find allies through violent domination. A high ranking female has first access to resources and females in general determine who the alpha male is by which male leads the group to the best resources. Females have the power to oust an alpha male who doesn’t fulfill this imperative. As a society, chimpanzees long ago developed hunting strategies that included cooperation, and were guided by influential, high ranking individuals. Chimpanzees are tool makers. They have been observed using digging sticks and spears, used to both acquire food and create a social display. They have also been seen sharpening their teeth. Both aggressive and territorial, chimpanzees have been known to kill their own species and often target lower order primates in their hunts. The meat is used as a status symbol to accrue greater community approval.

Chimpanzees are highly communicative and have a complex language that includes hand gestures, vocalizations, and facial expressions. At night they build nests in trees that provide comfort and security from predators. This skill is taught to infants by their mothers. They can be altruistic too and have been known to adopt both male and female orphans even if those orphans originate from a different group. Chimpanzees have been observed sharing food, forming coalitions, cooperating in hunts, and guarding their territory. They demonstrate having the ability to play, mourn, cultivate romantic love, express joy, appreciate natural beauty, and respect other wild species. The wide range of behavior exhibited by chimpanzees is hauntingly human, both good and bad, and suggests looking into remote history lends some impressive insight into our own natures.

Chimpanzees and humans share a matrilineal ancestor and we can find the last chimp-human ancestors alive about 5 to 7 million years ago. Individuals found to date include: Ardipithecus, Sahelanthropus, and Orrorin.  It is believed that different chromosomes split at different times over a period of perhaps 4 million years. This could make it impossible to a fix a specific date to specialization because of wide spread hybridization. Time and many more finds might provide the answer some day.

Sahelanthropus is an extinct individual of the Hominid family from 7,000,000 years ago. He was bipedal and likely a tree dweller as well. Sahelanthropus is to date the oldest known human ancestor after the split from genus Pan. However, it is possible he is related to both genus Homo and genus Pan while not being an ancestor of either.

Orrorin, another extinct bipedal tree dweller has been dated to 6.1 to 5.7 million years ago.  He is more anatomically similar to humans than the famous Lucy (Australopithecus). His reduced canines suggest a more intelligent, socially conscious individual. Orrorin apparently didn’t live in the savannah but found his way in a dry evergreen forest habitat.

Ardipithecus as another bipedal, tree dwelling species had his day 4.4 to 5.6 million years ago. His feet provide evidence that he was far more accomplished at walking than chimpanzees. Like Orrorin, Ardipithecus had much smaller canines suggesting he was an omnivore and frugivore. Perhaps greater significance can be found in the fact that smaller canines suggest less male to male conflict, increased pair bonding, and greater parental investment. Ardipithecus lived in a mosaic of woodland, grasslands, lakes, swamps, and springs.

Of these ancient ones Australopithecus, commonly known as Lucy, is probably the best known species. She and her relatives lived about 4,000,000 years ago and disappeared about 2 million years ago. That is an impressive reign considering Homo sapiens sapiens, us, have only been around a mere 200,000 years and are probably well on our way to extinction already. One of the Australopith species, A. africanus, evolved into the Homo genus. Candidates include Homo habilis, H. erectus, and H. ergaster.  One of these fellows sired the Homo sapiens line; it is also possible all of them represent a stage in that line.

Australopithecus, Lucy, is the first known true bipedal, a common ancestor to both Homo and Paranthropus, who co-existed. Although she shared both human and ape traits, she is the first to illustrate that large brains didn’t precede bipedalism. Lucy ate fruits, vegetables, tubers, and meat. Evidence has been found that shows she was an accomplished tool maker, crumbling the previously held notion that genus Homo was the first to make such tools.  Bones, 3.4 million years old, have been found that show distinct and unmistakable marks of having been butchered, complete with cuts, scratches, scrapes, and percussion marks made by stone tools. Fragments of those tools were actually found in the bones. Genus Homo didn’t show up for almost another million years. Because no manufactured tools have yet been found it remains unclear if Lucy actually made tools or simply exploited something handy from her surrounding environment.  The recent find of butchered bones suggests that group scavenging and the use of tools likely spawned the crucial development of teamwork due the group’s exposure to predators and the need for efficient cooperation while remaining alert to surrounding threats.

Paranthropus is perhaps the saddest evolutionary experiment. His teeth show that he was our most vegetarian ancestor. He was primarily an herbivore that ate nuts, seeds, vegetables, and grubs. Paranthropus inflexible diet drove him to extinction because he was unable to adapt to climate change and the territorial pressure it caused. He was a full bipedal that lived in the forest. When that forest became savannah Paranthropus simply lacked the resourcefulness needed for adaptation even though he had a larger brain than Australopithecus. Although by far the most outstanding herbivore found to date it should be noted that eating grubs makes an individual an omnivore.

Kenyanthropus was also a short lived, diet driven experiment from 3.5 to 3.2 million years ago.  He and Lucy co-existed, filling new ecological niches in that environmental mosaic described earlier. While Lucy went on, Kenyanthropus didn’t make it after only a rather brief debut.

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Responses to “2. Some of Our Oldest Relatives”

  1. Angela Cheetham Wilkinson June 7th, 2013 - 11:36 am

    How can I become a bonobo? Non-violent, matristic and egalitarian sounds like an improvement rather than a backward step. The word ‘matristic’ is unfamiliar to me – do I understand it to mean ‘matriarchal’?
    I particularly like your writing about Lucy and her hands, damaged by tools but we know not whether she made them – as you always remind us – we don’t know yet – but that doesn’t mean we never will – whilst recognising that the ‘we’ we refer to might well be extinct before we reach that state of knowledge.

    • Matristic is word first created by Marija Gimibutas in effort to draw us away from the implied superiority of the word matriarchal. Its a word I really like.
      With regard to Lucy, my guess is that she was clever enough to simply pick up what she needed rather than actually manufacture a tool. Lucy was a free and independent woman. I can’t envision her burdening herself with a tool that had to be lugged around.
      The bonobo has been an extremely successful species hasn’t she, happy with her egalitarian lifestyle for millions of years. I often think that our species and its long line of relatives have perhaps never been happy, always striving to be better, setting our sites on greater and greater achievements. Bonobo has always been there, right beside us and yet we failed to see the beauty of her life as a possible role model for our own. I don’t think of her as a step backward but rather far more evolved. The criteria set for measuring evolution is one we created to suit ourselves, to perhaps glorify the human species in a way that makes us appear to be the top of the heap. But we only need to look around to know that that isn’t true.

      • Angela Cheetham Wilkinson June 8th, 2013 - 10:02 pm

        That’s a loving and rather moving response and, although I haven’t a tittle or jot of your knowledge on the subject, I’m in such wholehearted agreement on your position with regard to the false and mighty place we position ourselves in – ‘the top of the heap’. Even as we assume the position we are tumbling into an abyss of our own creation. Welcome back bonobo?