Extent of Mutational Capability

CRR writes:Although some people may wish for a black-and-white criterion for defining species, this is unrealistic.

The definition I favour is "those animals/plants that could interbreed immediately following creation".

CRR writes:I have provided a definition of kind as per Percy's request [#45] and in response to others. The definition I favour is "those animals/plants that could interbreed immediately following creation". You might not agree with it but you now have one.

RAZD writes:You can also throw Homo neanderthalus in the mix as sister species in clade Homo, closer to H.sapiens than the Pan clade.

RAZD writes:Where C is not the same as A, but is a braided mosaic of B and D. Note that A, B, C and D still form a clade descended from A.

Taq writes:What we do have is genetically distinct populations that did occasionally interbreed.

Taq writes:The best answer, IMHO, is that they were separate species.

Taq writes:Of course it still means something. It means that limited interbreeding is producing statistically significant genetic divergence which can be objectively measured.

1. If there was free interbreeding then they would fall into the range of variation for modern humans. They don't.

2. They were recognized as not being anatomically modern humans when we first found them. Time isn't going to change that.

CRR writes:It's known as Haldane's Dilemma. A clear exposition is given in http://saintpaulscience.com/CostTheory1.pdf

Claim CB121:J. B. S. Haldane calculated that new genes become fixed only after 300 generations due to the cost of natural selection (Haldane 1957). Since humans and apes differ in 4.8 107 genes, there has not been enough time for difference to accumulate. Only 1,667 nucleotide substitutions in genes could have occurred if their divergence was ten million years ago.
Source:ReMine, Walter J., 1993. The Biotic Message, St. Paul Science, Inc.
Response:Haldane's "cost of natural selection" stemmed from an invalid simplifying assumption in his calculations. He divided by a fitness constant in a way that invalidated his assumption of constant population size, and his cost of selection is an artifact of the changed population size. He also assumed that two mutations would take twice as long to reach fixation as one, but because of sexual recombination, the two can be selected simultaneously and both reach fixation sooner. With corrected calculations, the cost disappears (Wallace 1991; Williams n.d.).Haldane's paper was published in 1957, and Haldane himself said, "I am quite aware that my conclusions will probably need drastic revision" (Haldane 1957, 523). It is irresponsible not to consider the revision that has occurred in the forty years since his paper was published.ReMine (1993), who promotes the claim, makes several invalid assumptions. His model is contradicted by the following:
The vast majority of differences would probably be due to genetic drift, not selection.
Many genes would have been linked with genes that are selected and thus would have hitchhiked with them to fixation.
Many mutations, such as those due to unequal crossing over, affect more than one codon.
Human and ape genes both would be diverging from the common ancestor, doubling the difference.
ReMine's computer simulation supposedly showing the negative influence of Haldane's dilemma assumed a population size of only six (Musgrave 1999).
Links:Williams, Robert, n.d. Haldane's dilemma. http://www.gate.net/~rwms/haldane1.html
References:Haldane, J. B. S., 1957. The cost of natural selection. Journal of Genetics 55: 511-524.
Musgrave, Ian, 1999. Weasels, ReMine, and Haldane's dilemma. The Talk.Origins Archive Post of the Month: September 1999
ReMine, Walter J., 1993. The Biotic Message, St. Paul Science, Inc.
Wallace, Bruce, 1991. Fifty Years of Genetic Load - An Odyssey. Cornell University Press. See particularly Chapters 5, 6, 8, and 9.
Williams. (See above)