Thursday, August 11, 2011

Missing links

Domestic animals sometimes become feral animals, and interbreed with compatible wild animals. Conversely, hunters sometimes introduce wild game animals into foreign habitat. These animals sometimes interbreed with compatible native wild species or compatible domestic livestock. Or sometimes exotic pets escape. Or owners dump exotic pets when they become too much of a handful.

To take some concrete examples, wild boar, which were introduced into North America, interbreed with domestic pigs. Lions and tigers sometimes interbreed–producing ligers.

In South Florida, there’s a concern that Burmese pythons may interbreed with African rock pythons. And you also have reticulated pythons in Florida. Dingoes are another example. And Africanized bees.

Or compare feral horse with wild horses.

This raises a question: if an evolutionary biologist were examining the fossil remains of hybrids, how could he tell the difference between a hybrid and an intermediate or transitional species?

Suppose he had fossil remains of lions, tigers, and ligers. In principle, you could have four competing evolutionary trees:

i) Lions evolved from tigers–via ligers

ii) Tigers evolved from lions–via ligers

iii) Ligers evolved from lions and tigers

iv) Ligers were the common ancestor of lions and tigers

How does an evolutionary biologist distinguish evidence for transitional/intermediate species from evidence for hybrids?

Wouldn’t a hybrid share characteristics of two distinct taxa? 


  1. Shouldn't the titled be named "Missing Lynx"? ;^)

  2. He really couldn't without a full DNA sequencing and a reference for populations of existing species before and after. Often all paleontologists can do is look at morphology and relative strata (assuming geological uniformitarianism). Then they make evolutionary speculations from naturalistic presuppositions. After all this, the speculations are confused as being conclusions and are used to tout the fossils as evidence for evolution. Does that sound about right?

  3. Actually it does. I stand corrected, sir. ;^)

  4. "evolutionary speculations from naturalistic presuppositions" ... as opposed to what? The wave of a wand?

    The author of this post is one of the smartest theological writers I have come across on the web. However, I am uncertain as to whether he has a basic understanding of mitochondrial DNA. My understanding is that examination of mitochondrial DNA is how evolutionary biologists definitively establish lineage. Without DNA samples, it appears to be much more of a guessing exercise based on examination of similarities between fossils.

    If someone could point me to a post on this site which explains where fossils came from (assuming that onhe accepts the Bible as the literal word of god),I would be grateful. Best, TAM.

  5. "... as opposed to what? The wave of a wand?"

    We all have our presuppositions. It's telling that you would mischaracterize divine creation as the "wave of a wand". That's not the best way to convince authentic Christians of the nonexistence of a Creator.

    Mitochondrial DNA (mtDNA) has been used to trace recent population movements for various species, particularly humans. But that also assumes that females only remain in their core populations. Inasmuch as populations are mixed - and for ancient humans this can entail concubines from conquered populations - the results would be skewed.

    However, assuming genetic drift is true, populations of divergent species could contain similar mtDNA such that one would wonder if one came from the other or if one was the ancestor of the source population when it wasn't. The only way would be to discover the specific mutations. Since this has never been done on ancient populations and there hasn't been enough time among recent populations that we can test to definitively determine genetic drift, we're really buried in a sea of speculation.

    But what really confuses the issue as this article points out is that ancient natural hybridization could be easily confused as transitional states. Even if you could look at their mtDNA you would either be doubly confused or be forced to conclude hybridization because the mtDNA would be the same as the population species of the mother. There's no way the evidence can support the conclusions unless divine creation is a priori excluded from consideration. And I think that's ultimately the point.