Chimps and humans: what’s in a name?

Whether we classify chimpanzees as pan or homo is a matter for evolutionary biology - not morality.

Chris Pile

Topics Science & Tech

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‘Could a chimp ever be charged with murder?’ thunders the headline in the Daily Mail, reporting new research into the evolutionary relationship between chimps and humans. The article continues to consider ‘The moral question posed by a campaign to classify some apes as human’ (1). But we should be wary of attempting to draw moral conclusions from scientific findings.

The story reports the results of a new study led by Soojin Yi at the Georgia Institute of Technology, Atlanta, that provides new evidence that chimpanzees are more closely related to humans than they are to the other great apes. The researchers analyzed DNA from humans, chimps, gorillas and orangutans to look at the speed of their ‘molecular clocks’ – the rate at which genetic changes occur over time. The speed of the clock reflects how the generation time – the length between each generation – has changed over the millennia. Their results show the rates of genetic change in humans and chimps to be very similar and much slower than those of the other great apes (2).

The researchers go on to suggest that the pace of evolution has been so slow since humans and chimps split from their common ancestor, that distinct human-specific traits, such as bigger brains and longer gestation periods, have only begun to emerge in the past million years. In other words, humans and chimps could be even closer in evolutionary terms than we had previously thought.

All very interesting but where’s the story? It’s pretty much accepted within the scientific community that humans and chimps split off from a common ancestor around six million years ago, making us more closely related to each other than we are to any other primate. The findings add evidence in support of the prevailing consensus but there is little qualitatively new here.

But then Dr Yi fanned the flames of publicity by linking her group’s findings to the controversial proposal to scrap the chimpanzee genus Pan and to reclassify its members under the Homo genus alongside humans. She was quoted as saying: ‘This study provides further support for the hypothesis that humans and chimpanzees should be in one genus, rather then in two different genus’, because we not only share extremely similar genomes, we share similar generation time (3).

There has long been confusion over how best to classify the two species of chimpanzee (the common chimp, Pan troglodytes, and the promiscuous bonobo, Pan paniscus). When the chimp was first classified by Carl Linnaeus in the eighteenth century, he originally placed it alongside humans in the Homo genus on the basis of shared traits such as the possession of opposable thumbs, and of flat fingernails and toenails instead of claws. Later taxonomists proved less welcoming, however, and the chimp was reclassified in 1816 into its own genus, Pan, where it has remained until this day.

In 1991, the ecologist Jared Diamond made the case for reclassification in his book on the recent evolutionary history of mankind, The Rise and Fall of the Third Chimpanzee. By 1999, changing views on the status of great apes led to an attempt to force the New Zealand government to pass a bill conferring certain ‘rights’ on to chimps and the other great apes. The British chimpanzee expert Dr Jane Goodall spoke at the time of using the issue to break ‘the arrogant perception that most people have that we are totally different’ and hoped that the campaign would extend the ‘circle of compassion, first of all to our closest living relatives’ (4).

The campaign was derided by many but succeeded in winning great apes legal protection from experimentation, and activists in the USA launched a similar effort in 2002 (5). More recently a study by scientists in the USA found that 99.4 per cent of the most critical DNA sites are identical in human and chimp genes, causing the lead researcher, Morris Goodman, to call for the reclassification of chimps and humans under the genus Homo (6).

Although the issue of reclassification is admittedly of great interest and importance to many evolutionary biologists, at one level it is primarily about semantics. A change in the nomenclature used to describe a species – whether it be human or ape, bird or plant – doesn’t in itself tell us anything new about that species, nor should it require us to fundamentally reevaluate the way in which we see it.

However, in recent years the controversy about chimpanzee classification has taken on increasingly political implications. It’s no longer just about evolutionary biology, but has instead been taken as a marker of the moral equivalence of humans and chimps. The issue has been adopted by activists pushing for the abolition of all forms of animal experimentation, who see the reclassification of chimps from Pan to Homo as the first step in a campaign to extend rights to all animals. They argue that the ever-growing body of scientific research into human’s recent evolutionary history supports the case for the reclassification of chimps, and that reclassification will in turn make the moral case for extending certain rights to chimps that are currently reserved for humans.

The Daily Mail article encapsulates this argument when it asserts that, ‘to allow the two species of chimps to leap from the genus Pan to that of Homo would fundamentally alter our view of both apes and ourselves.’ It then goes on to tell us that reclassification will challenge ‘everything we think about what it means to be human’, the implication being that reclassification will mean moral equivalence between humans and chimps (7).

But such reasoning is flawed. This latest research tells us nothing new about how we should see ourselves and there is no justification for drawing moral conclusions from the findings. Analyses of DNA do not tell us how to view ourselves, or our place in nature. The idea of human-chimp equivalence is gaining ground in the context of a misanthropic cultural climate, where human attributes such as reason and consciousness are regarded with mistrust, if not disdain.

It is important that scientists are explicit about the limitations of their work. A good example of this was provided last year when the complete chimpanzee genome was published. Dr Francis Collins, head of the National Human Genome Research Institute which funded the project, announced: ‘As our closest relatives, they (chimpanzees) tell us special things about what it means to be a primate and, ultimately, what it means to be a human at the DNA level.’ But, he emphasised, the study does not address philosophical or religious questions (8).

It would indeed be ironic if one of humanity’s greatest achievements – the decoding of the human and the chimpanzee genomes – lead us to conclude that, under the skin, we are really just apes.

Chris Pile is a spiked intern.

(1) ‘Could a chimp ever be charged with murder?’, Daily Mail, 25 January 2006

(2) Evolution study tightens human-chimp connection, Georgia Institute of Technology, 24 January 2006

(3) Evolution study tightens human-chimp connection, Georgia Institute of Technology, 24 January 2006

(4) Apes in line for legal rights, BBC News, 11 February 1999

(5) US activists demand lawyers for chimps, BBC News, 26 April 2002

(6) Put chimps in human family tree, CBS News, 19 May 2003

(7) ‘Could a chimp ever be charged with murder?’, Daily Mail, 25 January 2006

(8) Gene map shows what makes us different from chimps, Reuters, 31 August 2005

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Topics Science & Tech


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