If you're going to criticise evolutionary biology, one of the best attested theories in modern science, then you need to do so from the position of one who knows the discipline intimately, that is, someone who has studied the subject formally, conducted research in the subject, and discussed your ideas with other scientific professionals. If you're a layperson whose knowledge comes from fundamentalist Christian websites, or the abstracts of scientific papers you've completely misunderstood, then no one will take you seriously. It's that simple.
That something this obvious needs to be emphasised is unfortunately a testament to how deeply fundamentalism, science denialism, and the misguided belief that "having the Truth" when it comes to theology automatically translates to mastery of every subject. I was reminded of these facts yesterday when I looked at an evolution denialist Facebook page managed by a Christadelphian with a modest background in philosophy who has acknowledged elsewhere his lack of formal scientific qualifications. That considerable deficit alas has not stopped him from pontificating in a spectacularly uninformed manner on human evolution, demonstrating in the process his complete ignorance of the subject.
A splendid example of this special creationist's monumental ignorance of the subject (hereafter identified as SCACP after his page which unimaginatively is named Special Creationism - A Christadelphian Perspective) can be seen in this post:
A few weeks ago I posted observing that Adam and Eve were not selected from an existing population of humans because there is no verb of selection in the account but verbs of making, forming and creating. I can now extend this point in the form of a challenge to theistic evolutionists/evolutionary creationists.
Adam and Eve are not specially created instances of human beings if there already was an existing population of human beings on the ground - there would be no need to create two instances - you could just select a pair from the existing population.
So, Adam and Eve must be specially created as the first of a species.
Ignoring the fact his post is simply hand-waving assertion, his claim that Adam and Eve were specially created as the first of a species is flatly contradicted by these facts:
- The considerable genomic evidence for human-ape common ancestry as demonstrated by multiple shared identical retroviral elements, retrotransposons, ectopic telomeric DNA, and scars of DNA repair at the same place in human and ape genomes.
- The fact that there is no evidence of a razor-sharp genetic bottleneck in the human genome
In addition, if Adam and Eve were the first of a species, then we would not see any anatomically modern human fossils prior to around 10,000 years ago which given that this is approximately when animals and plants were first domesticated in the Ancient Near East is the earliest possible date for Adam and Eve. Unfortunately for SCACP's assertion, we see evidence for anatomically modern human beings existing at least 195,000 years ago. SCACP is simply wrong, and the only option available for him is to concede this point, and abandon his theological motivation for denying the reality of human evolution.
Unfortunately, as the following exchange indicates, that his hardly likely:
If SCACP wants to be taken seriously as an informed participant in the evolution-creation debate, then he needs to understand the science intimately. That he tries to evade the burden of proof by asking his interlocutor "what material [had he] read on the bottleneck" is par for the course for evolution denialists, but the fact SCACP had to ask for a popular presentation immediately disqualifies him from taking part in the conversation. The burden of proof lies solely on SCACP to show that the scientific evidence does in fact support a bottleneck, and it is patently, screamingly clear that he doesn't even understand the subject at a popular level, let alone the level of advanced population genetics.
SCACP, if he really understood the subject, would be aware that "[g]enetic and fossil evidence largely supports a single, recent (<200,000 yr) origin of modern Homo sapiens in Africa followed by a later dispersal to the rest of the world (“Out of Africa” model." [1] He would also be intimately acquainted with the primary literature, of which the 2007 Genome Research paper is representative. This article determined a "[r]ecent human effective population size estimated from linkage disequilibrium" by examining data from "Yoruba from Ibadan (YRI), Nigeria; Japanese from Tokyo (JPT); Han Chinese from Beijing (HCB); and residents from Utah with ancestry from northern and western Europe (CEU)" and found that for:
CEU, JPT, and HCB, the estimate of effective population size, adjusted for SNP ascertainment bias, was ∼3100, whereas the estimate for the YRI was ∼7500, consistent with the out-of-Africa theory of ancestral human population expansion and concurrent bottlenecks. [2]
That is inconsistent with any special creationist belief that the entire human race derives exclusively from two people living several thousand years ago. The literature is considerable, and citing even a fraction of it not only would be well beyond the size limitations of a blog post, but be an example in thrashing a very dead special creationist horse, but another paper would not go astray. Li and Durban in a 2011 Science paper found evidence of two bottlenecks:
- Approximately 3 million years ago, with a reduction to around 10,000
- For European and Asian populations, a reaction to around 1200 between 20,000-40,000 years, while for African populations, this went to approximately 5700 around 50,000 years ago.
From a peak of 13,500 at 150 kyr ago, the Ne dropped by a factor of ten to 1,200 between 40 and 20 kyr ago, before a sharp increase, the precise magnitude of which we do not have the power to measure. We also observed a less marked bottleneck in YRI from a peak of 16,100 around 100–150 kyr ago to 5,700 at 50 kyr ago, recovering earlier than the out-of-Africa populations, with an increase back to 8,700 by 20 kyr ago, coinciding with the Last Glacial Maximum. All populations showed increased Ne between 60 and 200 kyr ago, about the time of origin of anatomically modern humans. [3]
The lack of a razor-sharp genetic bottleneck in our genome is entirely uncontroversial among those who actually understand the subject. As geneticist and evangelical Christian Dennis Venema notes:
what we see in the genetics of our species is unremarkable for a relatively large-bodied mammal – we do indeed share common ancestry with other species, and we descend from a large population that has never numbered below about 10,000 individuals throughout our evolutionary history. Scientifically speaking, these issues are straightforward and uncontroversial. [4]
One would hope that SCACP and the other science denialists in our community would have the good grace to accept this fact, and cease dragging our community further into obscurantist shame and ignominy with their hopelessly wrong attacks on the fact of human evolution.
References
1. McEvoy, B.P. et al . Human population dispersal “Out of Africa” estimated from linkage disequilibrium and allele frequencies of SNPs. Genome Res (2011) 21 (6) 821-829.
2. Tenesa, A., et al. Recent human effective population size estimated from linkage disequilibrium. Genome Res (2007) 17 (4) 520-526.
