Adaptive acquired characteristics are genetically primed but not assimilated

Post Author: John Jacob Lyons

In their book, “The Four Dimensions of Evolution”, the Waddington ‘canalization’ explanation of the genetic assimilation of adaptive acquired characteristics is referenced (p.262) and tacitly accepted by Eva Jablonka and her co-author, Marion Lamb. I don’t find this explanation at all convincing and want to propose my own explanation. I suggest that adaptive acquired characteristics are always positively and causally correlated with concomitant, genetically generated propensities. These propensities gradually become more prevalent in the gene-pool because of the success of the positively correlated acquired characteristic. In time, the organism will appear to be primed to acquire the adaptive characteristic. It is suggested that examples in humans are language and religion.

Suppose that a particular mutation (M) that appears at generation n increases the capacity to learn an adaptive behaviour (AB). AB will have a selective advantage and consequently the relative frequency of M in the population will increase in generation n+1. This will, in turn, increase the frequency of AB in this generation. So long as AB remains adaptive, this positive feedback loop will, over evolutionary time, lead to all organisms in the population having mutation M and exhibiting adaptive behaviour AB. Additionally, selective pressure will result in AB appearing earlier and earlier in the lifetime of organisms. In due course, it will appear that all organisms in the species are primed to acquire the AB.

As stated, I believe that two examples of this process in humans are language and religion. This would account for the innate ‘Language Acquisition Device’ hypothesized by Noam Chomsky and Precocious Religious Belief hypothesized and empirically demonstrated by, among others, Justin Barrett (Centre for Anthropology and Mind, Oxford University). I don’t believe that an adaptive acquired characteristic is ever genetically assimilated as proposed by Waddington. In other words, I don’t accept that the Weismann Barrier between somatic and germ cells is ever crossed in these circumstances. Rather it is as if the constituents of the genetic soil, as it were, are gradually optimized to promote the germination and growth of the AB seed. In the case of religion, the seed of belief/ faith may be provided by the parent explaining to the child that their sadly expired pet kitten, Tiddles, is now “with god in heaven” and reinforced by similar references later on. In language, the innate universal grammar proposed by Chomsky and others, may be characterized in a similar way with the heard phonemes, words, syntax and grammatical exceptions of the native language providing the seeds.

It is also suggested that the niche construction and extensions to phenotype seen in many species of animal may also have a similar origin. These could well have originated as behaviours that proved to be adaptive and that, eventually, resulted in the concomitant, positively correlated and genetically mediated allele-sets becoming ubiquitous in the species. These would then have primed the young organism to reproduce the behaviour with minimal exposure to the behaviour by others.

Advertisements

17 thoughts on “Adaptive acquired characteristics are genetically primed but not assimilated

  1. Ben March 25, 2009 / 6:44 pm

    One quick question: you suggest that this mechanism applies to religion – or at least some aspect of it (that captured by Justin Barrett’s work). Does this mean that you view religion – or at least this aspect of it – as adaptive? Your consolatory example seems similar to Dennett’s proposition that suggestibility may be selected for for its health benefits and I am wondering if you meant this or are simply referring to primers of belief in those with genotype M.

  2. John Jacob Lyons March 25, 2009 / 9:34 pm

    Thanks for that Ben.
    I am suggesting that the mechanism may apply to religiosity in general. Belief in the supernatural, including god(s), may well have been adaptive over a long period during the Environment of Evolutionary Adaptation (EEA) relevant to our species. It would have enhanced status in the group and higher status would tend to result in greater fecundity and protection for offspring. The genetically mediated and positively correlated precursors of this adaptive behaviour may have been intelligence/ creativity for example. This could then have started the positive feedback loop between successive generations that I have described.

  3. Ben March 25, 2009 / 11:40 pm

    Thanks very much for your post also.

    I can see how intelligence and creativity might be (naturally or sexually) selected for (perhaps through status gains as you state) and I can see how supernatural beliefs entail intelligence and creativity. But I guess I would still be interested whether supernatural beliefs (maybe just ideas) per se are adaptive. Am I correct to interpret your view thus: supernatural beliefs/ideas function as adverts for creativity/intelligence? Another interpretation: they allow effective manipulation of other (creative) minds. It seems that some argument is needed to link supernaturalism and status accretion.

    Another (non-exclusive) view is that supernatural beliefs are a byproduct of increased creativity (which may well evolve by the mechanism you propose). I think I tend towards this view, but I am not familiar enough with the evidence. Regarding the main thrust of your post (on assimilation), I completely agree – although separation of the germline is an innovation present in only some lineages (not in some plants for instance).

  4. John Jacob Lyons March 26, 2009 / 12:18 am

    More accurately, I suggest that it may have been the cultural expression of supernatural beliefs that was adaptive in early hominid groups for the reasons I have given. Any adaptive allele-set that predisposed toward such behaviour (eg intelligence/creativity) would then tend to be more prevalent in the following generation which would again result, statistically, in even more individuals expressing the adaptive cultural behaviour. Thus we get into the positive feedback accelerator that I am suggesting.

    At some point, I suggest that the adaptive genetic predispositions to; assume agency/intent in explaining unexpected events (teleological tendency), accept the guidance of parents and to seek attachment also became powerful drivers of the process I have described. I therefore suggest that the precocious religiosity found by Justin Barrett, Keleman and other researchers is the result of this process. Babies have been genetically primed for religious concepts; there is no genetic assimilation of religiosity as such.

  5. John Jacob Lyons March 26, 2009 / 11:37 am

    The expression of supernatural beliefs may well have been adaptive for both reasons that you suggest Ben. Status would also have been conferred by the reasonable assumption that the chosen conduit between the group and the powerful ‘god’ must, himself, possess power. This assumption is still among us today; is it not? I have in mind leaders of certain cults/sects some of whom sexually exploit their more attractive female followers.

  6. John Jacob Lyons March 27, 2009 / 5:02 pm

    I would like to use this ‘comment space’ to edit, refine and explain my original piece as necessary.

    My criticism of the Waddington ‘canalization’ explanation applies only to its use in the context of the, supposed, genetic assimilation of adaptive acquired characteristics; often called the Baldwin Effect. The explanation appears to be perfectly adequate, however, in accounting for the, empirically demonstrated, genetic assimilation of adaptive epigenetic changes.

    On p.289 of their excellent book, Eva and Marion invoke Waddington’s framework of genetic assimilation to explain the Baldwin Effect and this would appear to be incorrect. I am advancing a much more likely process to account for the observed Baldwin Effect and suggesting that genetic priming occurs rather than genetic assimilation.

  7. Ben March 27, 2009 / 9:44 pm

    I am interested by your statement that genetic assimilation of epigenetic changes is possible. What is your distinction between adaptive epigenetic changes and adaptive acquired characteristics in this context? As far as I am aware, while there is evidence of transgenerational epigenetic inheritance, there is nothing in animals establishing a flow of adaptive information from phenotype to genotype. Such a mechanism, if it exists, would need to discriminate adaptive from maladaptive changes occurring during ontogeny.

    Regarding religion again: I incline towards the byproduct view because it seems like the null hypothesis. In general I am a bit suspicious of models that posit multiple selective forces (although since the bottleneck adaptive change may have been accelerating). Although I can see your argument I think that sexual exploitation by charismatic leaders doesn’t require anybody to believe in a god.

  8. John Jacob Lyons March 27, 2009 / 11:29 pm

    I am very grateful for your continuing interest Ben.

    I am defining epigenetic changes as changes to the epigenetic markers/ methylation in cells during development that, I understand, occur in response to significant environmental changes. By ‘acquired characteristics’ I mean purely cultural changes in appearance, ability or behaviour. C.H. Waddington demonstrated genetic assimilation in Drosophila pupae exposed to high temperatures. The resulting phenotypes had crossviens in their wings missing. Apparently, they assimilated this characteristic genetically so that, after a number of generations, the abnormality consistently appeared even in the absence of the high temperatures.

    Do you agree that the process I have described could also apply to niche-construction? After all, NC is just a particular class of cases within the definition of adaptive acquired characteristics.

    Re.religion. Yes Ben, such sexual exploitation doesn’t necessitate genuine belief. However, it may be present for some of these guys as an aspect of their self-delusion. Like you, I also tend toward the explanation that emphasizes religiosity as a by-product of the adaptive inate dispositions that I mentioned above.

  9. john jacob lyons March 29, 2009 / 8:17 am

    Are birds from a nest-building species genetically ‘programmed’ to build their nests or they just genetically ‘primed’ to do so in the way I describe in my article above?

    Suppose eggs from such a species were artificially incubated and hatched to an environment in which nest-making
    material was collectable but not immediately ‘to hand’. Therefore, no immediate experience of a nest and no possibility
    of mimicking the behaviour of conspecifics. Would they build nests? (Please excuse any naivety from a theorist who has
    never carried out a biological experiment in his life.) Have any such experiments been carried out?

  10. Ben April 4, 2009 / 12:44 am

    Thanks yes – I have to be honest and say that I should look up Waddington’s study – it sounds interesting. I agree that your mechanism could apply to niche construction – although the latter is a perspective I am sceptical of (see this post for my reasons).

  11. John Jacob Lyons April 4, 2009 / 4:58 am

    The application to niche construction for any relevant species could be tested by empirically denying the possibility of access to the stimulus/’seed’ from the environment. Would the adaptive behaviour still occur? I would like to see such experiments take place but don’t have access to lab. facilities/ funding. Any ideas would be welcome.

    The reference for the Waddington paper is:

    Waddington,C.H.(1942),’Canalization of Development and the Inheritance of Acquired Characteristics’, Nature, No 3811, Nov 14, pp 563-565.

  12. John Jacob Lyons April 8, 2009 / 11:57 am

    I have suggested that we are genetically primed for both language and religion. We already know that humans and other ‘higher’ primates are genetically primed for empathy/love and that the behaviour will not be properly manifested in the absence of the necessary experiential trigger. It has been demonstated many times since Harry Harlow’s seminal experiments with monkeys in the 1950s that the necessary trigger is ‘secure attachment’. If I am correct, does this not add significantly to the potential explanatory scope of my ‘Genetic Priming’ hypothesis?

  13. John Jacob Lyons April 10, 2009 / 3:56 pm

    Additionally, I suggest that humans may be genetically primed for morality. Thus we may have a meta-theory for religiosity, language, love/empathy, morality and, possibly, some instances of niche construction.

  14. John Jacob Lyons August 7, 2009 / 4:31 pm

    Yet another aspect of human behaviour that may well have been encouraged by Genetic Priming is conscientiousness. In his recent book “Spent”, Geoffrey Miller writes “There may have been a positive-feedback loop between the domestication of other species and the evolution of human conscientiousness.” The domestication of other species would have been an adaptive acquired characteristic. Conscientiousness would have been a positively and causally correlated predisposition. In terms of Genetic Priming, Geoffrey is suggesting that conscientiousness may have been primed by the adaptivity of the practice of domestication.

    As I have said, an adaptive, acquired characteristic will never be genetically assimilated. What will happen is that selective pressure will result in the allele-configuration of the relevant subset of genes ‘trying’ to change in order to optimize the support given to the trait. However, in doing so, it may well be in competition with other adaptive traits ‘trying’ to optimize genes in the same subset to support them. This will obviously result in sub-optimization for any particular individual trait.

  15. Clifford Stevens September 19, 2011 / 11:22 pm

    There is no evidence in the Human Genome that the alleles of the Genome have any causal effect upon human behavior.

    The very concept of “priming” has no meaning in the genetic powers of the Human Genome, since the Genome is species specific and has reached the highest point of its optimization, An further optimization is futile and is based on a flawed observation.

    Father Clifford Stevens
    Boys Town, Nebraska

  16. Douglas Falknor January 29, 2012 / 8:34 pm

    Very interesting discussion, moved along nicely except for the end.
    I can hardly see how the small “g” genome “has reached the highest point of its optimization.” ? I didn’t get the Memo that the rate at which mutations occur had been stopped.

    JJ,

    Your genetically primed hypothesis–similar to one of mine that I’m calling “genetic infilling.”

    We come from an era when no one thought any aspect of religion could be inherited. I hope to help in some small way to raise an obscuring curtain and to show that genes will venture in any direction that raises no barrier, that genes will INFILL in any direction neutral to reproductive success, but remain and push forward in directions affording success.

    My hypothesis goes something like this: Hold all variables constant, besides selection at work, genes will infill and mimic cultural adaptations as long as there is no opposing selective pressure.

    Some aspects of behavior (see everyone for description of hyperactive agent detection device as a brain module, as well as predisposition to language, morality) could have genetically infilled given enough time and no opposing selective pressure.

    Genes, crudely at first, then over time, more closely approximate the genes which will ultimately present an expression more and more like the cultural adaptation it is mimicking.

    I lean toward a little more heritability of religiosity or spirituality. We had 100,000+ years for it to seep in our collective “soul.”

    Religions come and go (estimate in The Faith Instinct was 10,000 relgions, I think), we shouldn’t confuse the life cycle of particular religion with the more or less irrepressible drive for spiritual expression. We just need to find a better avenue for fulfillment that religion.

    (Love your blog, can you refer me to someone to tune mine up?)

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s