Are there whole orders of difference between humans and other animals?
Many behaviours that were at one time considered uniquely human – such as making tools, using symbols, cooperative hunting, food sharing, altruism, iconic gestures, politics, strategic deception, pharmacy, and even systematic warfare – have been demonstrated, one by one, in non-human animals. Scientists have been repeatedly forced to redefine what it is to be human. Some biologists now assert that there is nothing “special” about humans – the difference between us and other animals is of the same order as the difference between any species and another. We have “culture” the way elephants have trunks. But even if we look at our nearest relative – the chimpanzee – we find both “species differences” of the kind that makes any species unique, and whole orders of difference which distinguish humans and are largely or entirely unprecedented in chimps and other animals. This indicates a phenomenon known as emergence – the revolutionary appearance of a whole new way of organizing things, even including new and accelerated forms of evolution [ see species_differences and different orders of difference ].
Some of these are obvious to the eye or easily demonstrated – for example, chimps are hairier than us, they knuckle-walk as opposed to being truly bipedal, their hands are not so adapted to making and using tools, they are at least three times stronger than we are, and their brains are about three times smaller. During human evolution, since we learned to walk on two legs, there have been two periods of brain expansion with a phase of “gracilization” during the second, and a third period of brain contraction. Gracilization – a progressive loss of muscle and bone mass – suggests that our ancestors evolved a relatively leisurely life-style and were more cooperative than non-human apes, and certainly does not suggest that they were any more violent. It is commonly assumed that brain expansion was mainly driven by selection pressure for increasing “intelligence” or even language, but there are serious grounds for questioning this [ see the social brain and human evolution ]. Other species differences are not so obvious – for example, no chimp father can know who his children are. That is because, when a female chimp is in the fertile phase of her sexual cycle, she tends to mate with all comers, and “sperm competition” determines who gets to be the father of her child. This effectively prevents chimps from ever evolving anything like human culture, characterized by marriage and fathers who contribute to child care. Chimps also do not menstruate – they signal the fertile phase of their cycle, whereas human females conceal ovulation (even the woman herself seldom knows for sure when she is ovulating) and signal the infertile phase by menstruating. Further, human females are sexually receptive throughout the sexual cycle: that is, human sexuality serves functions other than reproduction – notably, bonding between sexual partners. That is one reason why human sexuality is often far more playful and experimental than sexuality in other animals, and perhaps why we are so prone to “deviant” forms of non-reproductive sex. It has been argued that concealed ovulation and continuous sexual receptivity in human females favour monogamous mating behaviour and paternal input into child care. But it is also possible that, in our hunting and gathering ancestors, menstruation may also have served such a function (see human evolution).
Different orders of difference
Species differences distinguish one bacterium from another, but the difference between a bacterium and a cow is something much greater – a cow represents a whole different way of organizing things. Whereas a bacterium is a single cell (a society of “cooperating” molecules) which is in competition with other such cells, macrobiotes – multicellular organisms such as oak trees and cows – are societies of cooperating cells, most of which commit genetic suicide so that a tiny minority – the sex cells – get to reproduce themselves and create new societies of cells. This is an example of kin-based altruism [ see human cooperation ] – non-sexual cells can afford to forego sexual reproduction since their sister sex cells perpetuate their genes on their behalf. In this case, societies of cooperating cells compete with other societies of cooperating cells within a particular ecological niche (cows compete with other herbivores but do not compete with oak trees). What changes from one level of organization to the next is the level at which cooperation and competition occur, and humans differ from non-human apes in this sense. The highest known levels of cooperation and competition are found in humans. Cooperative human endeavours (such as going to war) may engage millions of genetically unrelated individuals, and competition occurs at the level of international corporations and nation states. Each level of cooperation and competition – virus, bacterium, cow, or human – represents an emergent new order with its own structural logic and top-down causality (controlling the selfishness of its constituent parts). Biologists John Maynard Smith and Eors Szäthmáry (1995) refer to the appearance of new orders as “major transitions” in evolution. Examples include the emergence of chimerical modern cells (created when macrobacteria ingested purple bacteria – which became the mitochondria of modern cells – and green algae – which became the chloroplasts in plant cells), sexual reproduction (the precondition for multicellular organisms), and human culture. Major transitions, they point out, are few and far between because they depend on cooperation. The benefits of cooperation are long term, so the short- term goals of selfish individuals tend to resist such changes. When major transitions do occur, they are “big bang” events affecting entire communities simultaneously. An old biological order has to be overthrown and replaced with a new one – that is, emergent orders are always “anti-biological” relative to the previous order, just like human culture. But the human difference implicates not just one but a whole series of major transitions, each of which represents a “different order of difference” relative to non-human apes. Human culture itself could not have emerged without the prior emergence of self-consciousness, associated with an extraordinary richness and variety of social displays [ see human culture, the social brain, and human evolution ].
Maynard Smith, J., Szäthmáry, E. (1995) The Major Transitions in Evolution (Oxford: W.H. Freeman)
One difference that biologists find difficult to explain is human cooperation. According to current “selfish gene” theory, only two kinds of cooperation (between members of the same species) can evolve by genetic point mutations. One is kin-based altruism (Hamilton, 1967), and the other is reciprocal altruism (Trivers, 1971). “Altruism” refers to any act which benefits the reproductive potential of another individual at the reproductive expense of the actor. It makes sense to help close kin because many of the genes they pass on to their offspring are likely to be the same as yours. Kin-based altruism pays off if Hamilton’s rule is satisfied viz: rB > C, where B is the benefit to the recipient, C is the cost to the donor, and r is the coefficient of relatedness (which reflects the proportion of genes from a common source that two individuals are likely to share). In the case of identical twins r would equal 1(because, apart from the odd mutation, all their genes are the same); between other siblings or between a parent and child r would equal ½ (because a child inherits half its chromosomes from each parent); between a grandparent and grandchild, or nephew and uncle, r would equal ¼, and so on. An example of kin-based altruism is breast feeding in mammals. Reciprocal altruism means helping another who is likely to help you in return (“you scratch my back, I’ll scratch yours”). One example of this given by Dawkins (1989) is the blood-giving behaviour of vampire bats. When the bats return after a night’s hunting, those who are still hungry will beg from others, and a sated bat will regurgitate blood into the mouth of the hungry one. These bats bear “grudges” – if one gives blood to another who fails to reciprocate on a later occasion, the “cheated” donor will not give blood to that individual in future. Human cooperation transcends the limitations imposed by selfish genes. For example, following the 9/11 attack on the Twin Towers, rescue workers risked (and sacrificed) their lives rescuing people who were complete strangers, from whom they expected nothing in return. This is known as “generalised altruism”. Current Darwinian theory offers no explanation for this, but it cannot be a coincidence that all human societies are structured by formal systems of “exploded” kinship and reciprocity [ see human culture. The creation of such artificial systems goes a long way towards explaining human morality and large-scale cooperation, but does not explain compassion or why we find altruistic behaviour emotionally satisfying. One likely reason for our innate predisposition to altruism is role-play [ See Self/Other-Consciousness ]. During childhood (and beyond), we role-play others and so learn to identify with them and share in their experiences. So, for example, when we read a novel or watch a movie, we want the hero or heroine to succeed – we hope for a happy ending – because the protagonist’s happiness makes us happy, and his or her pain is also painful to us.
Dawkins, R. (1989) The Selfish Gene (Oxford: Oxford University Press)
Hamilton, W.D. (1967) ‘Extraordinary sex ratios’ Science; 156: 477-88
Trivers, R.L. (1971) ‘The evolution of reciprocal altruism’ Quarterly Review of Biology; 46: 35-57
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