Human Evolution

The discovery of the oldest known fossil hominid in Africa has raised once again the problem of human origins.

‘Toumai Man’ was unearthed in the middle of the Djurab Desert in what is now northern Chad. Not only was it found a thousand miles away from the expected location of early hominids (a region stretching from Southern Africa to the Great Rift Valley), but, dated between six and seven million years old, it was 3 million years older than the next oldest hominid skull.

In his article in the Independent, science editor Steve Connor writes that the discovery “could lead to a fundamental reappraisal of human origins and a radical rethink of the increasingly complex ancestry of man”.

The ‘radical rethink’ concerns the popular ‘linear’ model of human evolution which depict man’s journey as a series of smooth transitions from knuckle-walking hairy simian to bipedal ‘naked ape’ (‘complete with briefcase and rolled umbrella’ as Connor puts it). The discovery of Toumai man vindicates the view that human origins are a far more messy affair.

“Instead of a simple ‘tree of life’, there were many dead-ends and blind alleys with perhaps dozens or even hundreds of our ancestral cousins becoming extinct, including, perhaps, Toumai man himself.”

As Bernard Wood, one of the world’s leading anthropologists, writes today in Nature: ‘Here we have compelling evidence that our own origins are as complex and as difficult to trace as those of any other group of organisms’.

The simple, linear model of human evolution with a step-wise change leading to new species with ever-more-human characteristics has now been replaced by a more untidy or ‘bushy’ model as successive ape-like creatures acquired different kinds of human-like attributes.”

The model proposes hundreds of proto-hominid species, each developing different kinds of hominid adaptations (bipedalism, manual dexterity, a large brain) but for one reason or another succumbing to extinction.

But if human beings are the ‘dominant’ species on earth, how is it that acquiring human characteristics led so frequently to evolutionary dead ends? How often does one find only a single species remaining from a lineage, when that species occupies every corner of the globe?

Freud would not have been surprised at this result. Risking the accusation of teleology he may have pointed out that it is extremely difficult to create a human being. Freud often used the word ‘momentous’ to describe the changes which were crucial to human evolution, and he would have hardly been surprised that such an unlikely event happened only once.

He would have been disappointed, however, that, leaving no trace in the fossil record, some of the striking and unique features of ‘Homo sapiens’ seem to be ignored by the paleoanthropologists. The most important of these is our bizarre sexual constitution and behaviour. In Inhibitions, Symptoms and Anxiety he writes:

“We have found that the sexual life of man, unlike that of most of the animals nearly related to him, does not make a steady advance from birth to maturity, but that, after an early efflorescence up till the fifth year, it undergoes a very decided interruption; and that it then starts on its course once more at puberty, taking up again the beginnings broken off in early childhood. This has led us to suppose that something momentous must have occurred in the vicissitudes of the human species which has left behind this interruption in the sexual development of the individual as a historical precipitate” (SE Vol 20, p155)

These momentous events concern the origin of ‘culture’ and are co-terminus for Freud with the prehistory of the Oedipus complex. They required some difficult biological changes in sexuality in order to be effected.

Freud’s paleontology of the invisible gives us a different perspective on human evolution. We can now imagine a large-brained, upright, dextrous proto-hominid, making tools and hunting cooperatively, which still had not a snowball’s chance in hell of evolving into ‘man’, being unable to negotiate these biological hurdles.

In his last book, An Outline of Psychoanalysis, Freud mentions some of the ‘biological changes in sexual life’ which were necessary precursors for hominisation. As well as the function’s diphasic onset he includes “the disappearance of the periodic character of sexual excitation and the transformation in the relation between female menstruation and male excitation”.

That is to say, male sexual interest was no longer governed by olfactory signals given off periodically by the female, but occurred at all points in the females reproductive cycle (presumably including pregnancy and breast feeding).

A moments thought will reveal how momentous and difficult these changes would have been.

The fact that any species could have evolved to cope with their catastrophic effects is a miracle in itself. The fact that most biologists prefer stories of human evolution which include no ‘momentous events’ is less surprising.

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