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) .
As per David, some pre-requisites are required for the evolution and development of languages as we know them.
Four conditions are suggested for developing explanatory models that may account for these linguistic phenomena. These include (a) a mechanism for reproducing complex cultural behaviors intergenerationally over extended time, (b) a sequence by which articulated wordings could evolve from nonlinguistic primate communication, (c) extension of the functions of wording from enacting interpersonal interactions to representing speakers’ experience, and (d) the emergence of complex patterns of discourse for delicately negotiating social relations, and for construing experience in genres such as narrative. These conditions are explored, and some possible steps in language evolution are suggested, that may be correlated with both linguistic research and archaeological models of cultural phases in human evolution.
Edmund Bolles summarizes this as below:
Rose’s four steps required for the growth and survival of language are:
- reproducibility: along with the “suite of biological adaptations” for speaking, there has to be some “mechanism” for precisely reproducing the language that happens to be spoken wherever one happens to be born. Many inquiries into language acquisition assumed this reproducibility is purely biological, but Roses insists that language is reproduced across generations “by cultural means.” In other words, children learn language from their elders. We will see on this blog that this explanation is not accepted quite as widely as a novice might think. One thing is clear, we got this skill after we said goodbye to the chimpanzee’s line of descent.
- exchangeability: Once speakers have the ability to reproduce words they can “exchange” them. Rose takes the idea of an exchange of words more literally than I do; thus he talks about “exchange behavior” in primates, but the basic idea of being able take and modify one another’s existing words to create new ones appears sound enough. The interesting thing about such interactions is that both parties in the exchange “get” it. The usage is understood as a bit of wit or cleverness rather than as an error, so wit too is something added to our species when we had parted from the surviving primates.
- extendibility: one very peculiar quality of humans is what a resourceful species we are, able to turn established tools to new tasks as the purpose demands. A digging tool becomes a backscratcher becomes a probe. Equally, we can extend the uses of our verbal tools. Thus, words which were surely first “exchanged” as tools for interpersonal actions could be extended for use in expressing ideas and then extended again to be used in thinking through some complex set of ideas. At this point biology is left in the dust as the role of language is extended at a pace that far outdistances plodding natural selection.
- combinability: the various extensions of speech can be combined to produce still more verbal wonders, such as stories and polite behavior that lets people negotiate delicate situations without giving offense. At this point we can speak of craft, maybe even artistry. Speech, thought, and culture has moved so far from its primate roots that the idea of common descent becomes surprising.
To me these bring to mind the more genetic and physical (as opposed to the cultural based that Rose presumes them to be) pre-requisites for language, in particular, and symbolic manipulation in general, that Premack had outlined recently. I had commented on the same earlier by integrating those with the existing stage-based developmental model of language evolution/development.
I’ll briefly recap the pre-requisites that Premack had identified:
- Voluntary Control of Motor Behavior. Premack argues that because both vocalization and facial expression are largely involuntary in the chimpanzee, they are incapable of developing a symbol system like speech or sign language.
- Imitation. Because chimpanzees can only imitate an actor’s actions on an object, but not the actions in the absence of the object that was acted upon, Premack suggests that language cannot evolve. .
- Teaching. Premack claims that teaching behaviors are strictly human, defining teaching as “reverse imitation” – in which a model actor observes and corrects an imitator.
- Theory of Mind. Chimps can ascribe goals to others’ actions, but Premack suggests these attributions are limited in recursion (i.e., no “I think you thought he would have thought that.”) Premack states that because recursion is a necessary component of human language, and because all other animals lack recursion, they cannot possibly evolve human language.
- Grammar. Not only do chimps use nonrecursive grammars, they also use only words that are grounded in sensory experience – according to Premack, all attempts have failed to train chimps to use words with meanings grounded in metaphor rather than sensory experience.
- Intelligence. Here Premack suggests that the uniquely human characteristics of language are supported by human intelligence. Our capacity to flexibly recombine pieces of sensory experience supports language, while the relative lack of such flexibility in other animals precludes them from using human-language like symbol systems.
To me, the Imitation and Teaching seem to be the cognitive mechanisms by which reproducibility of languages across cultures and generation is ensured.
Theory of mind abilities would definitely be utilized and instrumental in the process of excahngeability, whereby one can use tokens like words to exchange meanings. For this mechanism to evolve, an ability to understand that others have mental states that are similar to us is necessary and only then can one comprehend what that person means when he uses a particular token. Also, the mirror system , that might be involved in ToM module , may also be sufficient to explain the evolution of linguistic words from non-linguistic communication.
Grammatical abilities like recursion and ability to use metaphors can be directly mapped to the capabilities like combinability and extendability, whereby complex linguistic devices can be combined to produce complex discourses and novel metaphors used for extending the semantics associated with a word.
I’m quite intrigued and excited by such commonalities! Does this excite you too? Let me know via comments.
As per a recent scholarly article it seems that mammalian evolution may have been driven by the predatory presence of snakes. While some mammals adapted by becoming better snake sniffers, others developed immunities to serpent venom; while in the case of humans, the primates developed a good visual system to detect the snakes.
The other factor that drove human evolution (and hastened descent from the garden of eden after falling prey to serpent’s designs 🙂 ) was the fact that anthropoid ate fruits (substitute apples 🙂 ) and this frugivorus eating habit endowed them with enough-glucose-availability-in-the-brain to act as a pre-adaptation necessary to the evolution of brain matter required for visual acuity needed to detect snakes and take appropriate action.
I’ll try to summarize the arguments.
1. It is common knowledge that runaway arms-race between predators and preys lead to selective development of traits in a particular direction. For eg, the great cats and the antelopes, both developed systems for high speed chase and run-away and thus some of the fastest runners are either predators; like leopards or preys like the antelopes. What food (and energy one gets from it) also ensures who outnumbers whom in the arms race (the tiger wins!). The responses may not be symmetric, while Great Cats may develop claws and teethes, the antelope may develop antler ( though antler evolved more as species specific displays to attract opposite sex).
2. Snakes are one of the predatory species for mammals. Earlier snakes relied on Boa constriction method to kill the preys, but evolved venom about 60 mn years ago as their second weapon. Mammals reacted by either detecting them (in close range) by sniffing, or developing venom resistance etc.
3. Primates leading to Humans reacted by detecting motion (via MT and other motion detecting brain areas), color and other relevant visual stimuli to predict and detect the snake’s presence at close ranges and take appropriate areas.
4. The increased encephalisation (dependent on processing of more visual stimulus and reacting to it) was dependent on a previous adaptation related to fruit eating and abundant availability of glucose in brain.
5. The features of human vision like orbital convergence (leading to depth perception and 3D vision) are tuned for such snake -detection mechanisms.
6. The koniocellular pathway is crucially involved (among other tasks) in pre-attentional visual detection of fearful stimuli, including snakes and the evolution of this system points to snake-primate arms race pressures and how the primates adapted.
7. The Parvocellular pathway is also implicated in the study (as details and color are important for snake detection). Although the magnocellular is not , but I believe movement is also very crucial as snakes have a typical motion.
Lastly, while the analogy of the snake and the apple is quite relevant in the Christian mythology context, the snake is a revered creature in many mythologies (dragon in Chinese for example) and we in India celebrated Naag Panchami – a day when snakes are fed milk- a couple of days back.
Some parting notes:
1. In experiments with monkeys and humans it has become apparent that we have specialized fear associations for snakes. For example a young monkey, which sees another monkey as reacting in a frightened manner to say a plastic snake, would by even a singular exposure to such a display of fear, clear to have fearful associations with say the plastic snake. This association can be even when the observed behavior is seen on TV (and is recorded and not happening in real-time) Like the disgust reactions and avoidance-of-just-before-taken-food in response to a single vomit, it seems the avoidance learning for snakes is also built-in and can be triggered even by one exposure and by observational learning. Thus, there is strong evidence that we have specialized circuits for responding to snakes. It makes merit to assume that we should have for detecting too.
2. In Indian philosophy, one perennial question, focused on differentiating reality from illusion is differentiating snake for the rope. the rope in dark gives illusion of a snake, but we need to enhance our perceptions and awareness to realize that the fear of the snake is illusory and that the feared object is only a rope. This example, which is in ancient texts, is evidence of the importance of snake detection from prehistoric times.
Endgame: Can one identify from which book this drawing of boa constrictor and elephant is inspired?