Six Million Years of Power and Sex

We humans share 98.7% of our DNA with chimpanzees and bonobos, our closest relatives in the diversity of life on this planet. The common ancestor to all three of us existed around six million years ago. Chimpanzees and bonobos split into two species around two million years ago. This split appears to have coincided with a drastic reduction in the flow of the Congo River.

Today, chimpanzees are mainly found north of the Congo River in equatorial Africa. In the wild bonobos are found exclusively south of the river in the Democratic Republic of Congo.

Why do the two species remain apart? Because of the Congo River.

Chimpanzees are reluctant, or unable, to swim. Bonobos are also reluctant swimmers, although they do sometimes forage waist deep in water.

The Congo River is the deepest river in the world, the ninth longest, and the third largest by discharge volume. It is also very wide, up to 19km across at its widest point. No wonder reluctant swimmers, such as chimpanzees and bonobos, have not crossed from one side to the other during the past couple of million years. But that drop in flow about two million years ago was just enough to enable a band of their common ancestor to cross the river.

Thus, for the past two million years, chimpanzees and bonobos have been evolving along separate trajectories. They may have had a common ancestor but nowadays they display dissimilar behaviours and identities.

Chimpanzees have been studied for much longer than bonobos and hence less is known about bonobos than chimpanzees even today, especially in the wild. As we have a common ancestor with chimpanzees from six million years ago it has been tempting to identify some of our human behaviours as similar to that of chimpanzees, and to trace these comparable behaviours back to that common ancestor.

These studies suggested that our levels of violence and male dominance have their beginnings in our common ancestral heritage. We have been seduced into thinking that such behaviours are innate in our DNA.

However, more recent studies of bonobos are calling this innateness into question.

Bonobos have sometimes been labelled as the hippie chimp. Bonobos do tend to display less aggression and a greater degree of egalitarianism than their chimpanzee cousins. This rigid distinction however, is simplistic. The reality is much more nuanced. Bonobos do become aggressive, although their aggression usually does not go as far as killing one another, as it can do with chimpanzees. Furthermore, bonobo aggression in the male of the species is normally restricted to male-on-male aggression. Chimpanzee males, on the other hand, more often direct their aggression towards females. Chimpanzee males are also likely to coerce females into sex, whereas male bonobos do not.

A further distinction between the two related species is in the manner in which they go about reconciliation after such violence. Bonobos use sex. In bonobo society sex is used to build close relationships, to calm one another down, and to resolve conflict. Sex is also used by bonobos as a way of greeting strangers.

Bonobos can be thought of as xenophiles, whereas chimpanzees act more from a xenophobic stance. Bonobo clans enjoy meeting another, sometimes unknown, clan of bonobos. It is often the females of each clan that initiate this contact, usually with sex.

The ways in which chimpanzees and bonobos deal with power and sex are noticeably divergent. So much so that the noted primatologist, Frans de Waal, quipped that ‘…(chimpanzees) resolve sexual issues with power, while (bonobos) resolve power issues with sex.’¹

All of this, of course, raises questions about the level of violence, and male aggression towards females within our own human societies.

Can we, as was once time thought, blame our genetic coding for male violence within the Homo sapiens species? Has our evolutionary history predetermined that men should be dominant over women?

When we consider the differences between chimpanzees and bonobos, the answer is clearly not.

We (chimpanzees, bonobos, and humans) have a common evolutionary path, yet we find that the two species that split most recently (two million years ago) have developed quite distinct behavioural traits. This suggests that male violence and male dominance is not innate. It is instilled in large part culturally.

If culturally imparted, then it can be culturally immobilised.

Let us hope that it does not take another six million years for that to happen.

 

Notes:

1. Frans de Waal, Our Inner Ape, Granta Books, London, 2005