Thursday, 7 May 2015

Ignorance & Double-Think - The Bear Necessities of Creationism

Genetically isolated sloth bears rely on habitat corridors to connect populations -- ScienceDaily

This paper is interesting from an ecological point of view, illustrating as it does the importance of maintaining a diverse habitat in order to maintain biodiversity, but it also neatly illustrates something which creationists either genuinely don't understand or about which they feign ignorance.

One of the most annoying questions creationists keep asking, as though they imagine it to be a killer question which destroys the idea of evolution, is, "If humans evolved out of monkeys, why are there still monkeys?" The slightly more educated ones will use 'apes' instead of 'monkeys', but the underlying ignorance is the same. This question can only seem even slightly intelligent to those who have no idea how speciation by population isolation occurs.

To anyone with more than a small inkling of the mechanisms of evolution, this question leaves them nonplussed, not because it's unanswerable, but because it's difficult to know where to begin with someone that ignorant, who is almost certainly that ignorant through choice or is even feigning it for effect. It's not as though the concept is hard to grasp or requires an in-depth understanding of some obscure aspect of biology, so it's hard to blame even a generally low level of cognitive ability. It most likely reflects a general unwillingness to think and an over-eagerness to conform to group norms and show group affiliation in a fundamentalist, creationist culture.

The paper's authors studied the genetic makeup of five isolated populations of sloth bears from five tiger reserves in central India by collecting hair and fecal samples:

Abstract

Sloth bears (Melursus ursinus) are endemic to the Indian subcontinent. As a result of continued habitat loss and degradation over the past century, sloth bear populations have been in steady decline and now exist only in isolated or fragmented habitat across the entire range. We investigated the genetic connectivity of the sloth bear meta-population in five tiger reserves in the Satpura-Maikal landscape of central India. We used noninvasively collected fecal and hair samples to obtain genotypic information using a panel of seven polymorphic loci. Out of 194 field collected samples, we identified 55 individuals in this meta-population. We found that this meta-population has moderate genetic variation, and is subdivided into two genetic clusters. Further, we identified five first-generation migrants and signatures of contemporary gene flow. We found evidence of sloth bears in the corridor between the Kanha and Pench Tiger Reserves, and our results suggest that habitat connectivity and corridors play an important role in maintaining gene flow in this meta-population. These corridors face several anthropogenic and infrastructure development threats that have the potential to sever ongoing gene flow, if policies to protect them are not put into action immediately.


Map of the study landscape with locations of all sloth bear fecal and hair samples collected shown in blue dots.
What this illustrates is not only how an isolated population can begin to diversify genetically, but how, if there is limited population exchange, genes can flow between otherwise isolated populations. The important concept here is that genes flow, carried by individuals between populations. With enough gene flow, there is no possibility of genetic isolation being maintained long enough for the populations to diversify according to local conditions or genetic drift to the point where they can no longer interbreed.

Where there is only very occasional gene flow, or interbreeding is only possible in exceptional conditions, taxonomists may even consider them different species because they are functionally genetically distinct, or at least classify them as subspecies. The ultimate test of speciation is whether, if the populations ever come back into contact, they interbreed. If not, by definition, they are distinct species, yet nowhere in that process was there a single 'speciation event'.

Creationists need to invoke another fallacy and use double-think at this point, needing to pretend that somehow the evolutionary mechanism by which genetically isolated populations diverge to the point at which they are effectively different species is impossible, but the changes which lead to varieties and subspecies, and the fantastic rate of diversification required to give the range we see today in every species, from a founder population of two or three pairs a few thousand years ago, is entirely possible, whilst simultaneously claiming the entire process is rendered impossible by the Second Law of Thermodynamics (sic).

For example, from just the two or three pairs of 'bear kind', creationists must believe that not only the diversity seen in populations of sloth bears, brown pears, polar bears, grizzly bears, etc, etc, has evolved in a few thousand years, but so has the diversity seen between the different species, which are all really the same species even though they don't exchange genetic material and don't normally interbreed. Creationist need to use a lot of private definitions of terms like 'species', 'evolution', 'logic' and 'reason'.

The problem creationists have is that the real science of evolution doesn't fit well with the infantile parody they have been sold by creationist pseudo-scientist in order to give them reasons to doubt it and something idiotic to attack from a position of wilful, self-congratulatory, self-important ignorance.

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2 comments :

  1. As I was reading your article, my mind was wandering off to those charts we see of evolution's progress. You know, the ones that start with an image of an early ape and then sequence through prehominids and finally a man. I wonder if some poor souls think they are witnessing the metamorphosis of an individual rather than the gradual change in the descendants of populations over long periods of time.

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    Replies
    1. I think some of them do.

      Others seem to think evolution is a female of one species giving birth to a new species because of a random 'mutation'. Still others seem to imagine evolution is a species spontaneously self-assembling, fully formed, from some sort of soup. For reasons which aren't hard to work out, creationist pseudoscientists do nothing to disavow their victims of these misunderstandings and everything to encourage them.

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