An interesting discussion is going on at slashdot regarding the recent speculation of LSE theorist Oliver Curry, that Humans may split into two species, very much like the Elois and Morlocks conceived by H G Wells, as a result of mate selection.

As per the standard evolutionary theory of how new species are formed, it is posited that new species result form existing species, when interbreeding between two factions of the old species stops and genetic variations accumulate in isolation in the two species making them different from each other and making them further unavailable for interbreeding. The original lack of interbreeding resulting in a species split may be due to accidental genetic changes that make interbreeding troublesome or less likely (or make resultant children unhealthy and unlivable) or it may be a direct result of sexual selection and preferential mating. This theory of a new specie origination has also been experimentally verified in fruit flies.

Oliver theorizes, that sexual selection would become prominent in the near future and eventually lead to the bifurcation of the human species, and this bifurcation would be on intelligence/attractiveness lines, with more intelligent and beautiful (Elois) making one strata and the dim-witted and ugly (Morlocks) making the other strata.

This is not inconceivable as intelligence and attractiveness (things like height, beauty etc) have been found to covary in humans and people do take these factors into account while choosing mates.

An added twist to this provide by the fact that SES or wealth is related to intelligence and thus, the bifurcation would also happen along economic lines. Again, wealth and status are attributes that are heavily involved in mate selection.

But for this process to take shape, inter breedings have to be prevented, or become less and less probable and we know that we, as humans, are still not choosy and do interbreed frequently.

What could accelerate and freeze the process of genetic differentiation between the species is the modern genetic research that may once more lead to eugenics-style human-enhancement efforts, with rich having more of these tools at their disposal vis-a-vis the poor. This is exactly the point that Peter Singer makes in his editorial “Gene Therapy” in today’s TOI and comes to a similar conclusion that we may be doomed to a split down the line.

I had speculated on something similar some time back: but my reasoning was more guided by evolutionary pressures that our ancestors might have faced during the EEA and whether that had laid the foundation for the split of human lineage. To be precise, I had speculated that the different foraging styles that our ancestors adopted during the EEA had lead to the evolution of different personality traits consistent with that personality ( there was some research that indicated that a foraging style based on begging or nagging the compatriots incessantly to give food might have had low Agreeableness associated and resulted in the emergence of an Agreeableness trait). Further, once people started assuming a certain foraging and personality style, they might have interbred within that class leading to the emergence of that trait in that population.

Fortunately, once the EEA pressures were over the populations mixed with each other and thus the personality traits dispersed in the population. There is not much evidence to back this theory, but it highlights one important point: there has to be environmental pressure on the species that makes them breed selectively and leads to emergence of new traits. If humanity manages not to screw itself ( by nuclear catastrophe or whatever) , then I cannot see any environmental pressures that would enforce the lack of interbreeding. We can thus sleep assured that we are not going to split in two. There will always be that quirky beautiful lady that marries the dumb ugly squat- motivated solely by that elusive thing called love- and not giving a damn about confirming to the standard sexual selection model- as long as we can ensure that we do not subject her to the evolutionary pressures faced by her ancestors and which have become mostly useless since the time we humans have started controlling our environments.

Update : An interesting sum-up of all the prominent blog postings debunking this claim has been compiled by Coturnix at A Blog Round the Clock. It is interesting to note that while John Wilkins, disagrees with the analysis because he thinks that human speciation, if it happens, will happen due to isolation (Allopatric speciation) and lack of interbreeding and that sympatric speciation is not relevant to us; John Hawks takes a completely different take and assumes that if human divergance can take place, it would be most likely sympatric and requiring natural selection against intermediate phenotypes. He rules out the possibility of all Morlocks shipped to an island and being isolated as a likely scenario! He does mention some intricacies involved in assortative mating and sympatric speciation which are worth musing over. The take home is that we are not going to split!!
My own take, had more focussed on Parapatric speciation, in which environmental pressures are a key factor. Key and drastic environmental changes clubbed with partial isolation (occupation of niches by daughter species) and the resultant selective interbreeding is posited as the mechanism here, and does not require either complete geographic isolation of the two diverging species (required in allopatry) or the requirement that the those heterozygous at the differentiating gene locus have less reproductive fitness compared to those who are homozygous (the sympatry requirement) .

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