@Sean: So there are birds who prefer to mate with other …

Comment on An apology to PUC by Eddie.

@Sean:

So there are birds who prefer to mate with other birds who have a more “attractive” song? – a song that matches their own particular preference? How is this somehow a basis for species classification whereas more striking differences between human ethnic groups, to include mating preferences, are not?

Song is a reproductive isolating mechanism for many species of birds. Reciprocal playback experiments demonstrate that birds strongly prefer to mate with their own song type. If they don’t want to mate with each other they are reproductively isolated–which is the criterion of the biological species concept. There have been reports of hybrid Alder X Willow Flycatchers but apparently none have been confirmed.

As for humans, numerous studies have demonstrated that genetic variation among human populations is lower than that of most animal species. The genetic evidence indicates that there has never been strong racial differentiation among humans, at least in comparison with that of many non-human animals. A good review of this can be found here:

Tample, A. R. 2002. The genetic and evolutionary significance of human races. Pp. 31-56 in Race and Intelligence: Separating Science from Myth (J. M. Fish, ed.). Lawrence Erlbaum Associates, Inc., Mahwah, NJ.

I suppose there is the potential for speciation in humans to occur as a consequence of assortative mating among racial or ethnic groups, but considerable interbreeding has historically occurred wherever and whenever different racial or ethnic groups lived together, unless it was prevented by culture, which has a strong influence (e.g., miscegenation laws preventing interracial marriage weren’t abolished in the USA until 1967). Maybe assortative mating is based more on culture than biology. Several studies have demonstrated that the degree of assortative mating based on racial or ethnic groups has declined over the past several decades, which is more suggestive of culture than biology. Furthermore, as I mentioned earlier, assortative mating among humans is extremely complex, occurring for both biological and culture factors. Assortative mating occurs for several biological traits besides skin, hair and eye color/texture which we often associate with race and ethnicity, including height, weight and (especially) age.

Eddie Also Commented

An apology to PUC
@Sean:

Certain types of birds are certainly notoriously picky about choosing a mate – that’s a given. The choice can hinge on extremely minor differences in appearance or song or even nest building skills. Yet, at the same time, far more striking phenotypic differences, and even unique genetic differences, between various breeds of dogs or even between different human ethnic groups which have been established via some span of reproductive isolation are not classified as different “species”? Why not?

The “striking phenotypic differences, and even unique genetic differences” among different populations of humans and dogs are the results of random mutation, genetic drift, natural selection or (in the case of dogs) artificial selection–not “some span of reproductive isolation.” Humans don’t depend on the color or texture of eyes, hair and skin to avoid mating with chimps or apes, or even different groups of humans. When a female poodle is in heat, it doesn’t matter what “breed” a male dog belongs to, it is equally stimulated and could care less about the length, color or texture of eyes, hair, ears, snout, legs, tail, etc. The reproductive isolating method between dogs (genus Canis) and foxes (genus Vulpes) is likely based on olfaction rather than external morphology.


An apology to PUC
Correction: the author of the citation above is Temple, not Tample.


An apology to PUC
@Sean:

And where are such barriers for various cryptic species for which there is no readily apparent phenotype block to mating with the production of viable and fertile offspring?

For the benefit of those who perhaps are confused by the subject matter, cryptic species refer to two or more species that closely resemble each other to human eyes yet somehow recognize each other as distinct species. They may occur in sympatry (living together), parapatry (narrowly overlapping in range) or allopatry (geogrpahically separated). They never or seldom interbreed because some sort of a reproductive isolating mechanism other than external morphological appearance has “evolved” (if I can use that term here).

I earlier mentioned a classic example, the Alder Flycatcher and Willow Flycatcher, which occur sympatrically in northeastern North America and are virtually identical yet differ in their vocalizations. The distinctive vocalizations of each species represent a behavioral reproductive isolating mechanism that prevents an individual from mating with the wrong species. Many similar examples exist among birds.

Another classic example that I earlier mentioned is the Eastern Gray Tree Frog and Cope’s Gray Tree Frog, which are essentially identical but differ in their number of chromosomes, 48 in the former and 24 in the latter (providing a rare example of polyploidy among animals). Although sympatric throughout much of their ranges, they cannot hybridize because of the different numbers of chromosomes. They can recognize each other through their distinctive vocalizations, which represent a behavioral reproductive isolating mechanism.


Recent Comments by Eddie

Changing the Wording of Adventist Fundamental Belief #6 on Creation

SDA Bio Prof: The Bible makes multiple falsifiable prophecies about Nebuchadnezzar conquering Egypt, yet history never records it happening. Does this mean the Bible is effectively falsified?

Sean Pitman: Egyptians had a strong tendency not to record their losses… only their victories.

Sean, does that mean YOU personally believe Babylon conquered Egypt, just as predicted by two prophets? In the absence of any empirical evidence? If the Egyptians didn’t record their losses, why wouldn’t the Babylonians have recorded such a stunning victory?


Southern Adventist University opens Origins Exhibit

Holly Pham: One of the things that has always concerned me is that, according to what I’ve read, birds and reptiles have completely different forms of respiratory systems (flow-through vs. bellows) How is this explained by evolutionists?

Evidence from the vertebrae of non-avian theropod dinosaurs suggests that they, too, possessed unidirectional flow-through ventilation of the lungs. So, according to evolutionary theory, it evolved first in “primitive” non-avian theropods rather than in birds, and comprises one of many shared derived characters supposedly linking birds with more “advanced” theropods. However, I don’t think there is any evidence or even a hypothesis for a step-by-step process of HOW it evolved. Here is a reference:

http://www.ohio.edu/people/ridgely/OconnorClaessensairsacs.pdf


Southern Adventist University opens Origins Exhibit
@Bob Helm: Bob, if you send me an e-mail at sdabioprof2@gmail.com I will send you a pdf file of a 1991 article published by Chatterjee in Philosophical Transactions of the Royal Society B 332:277-342, titled “Cranial anatomy and relationships of a new Triassic bird from Texas.”

Curiously his description is based only on cranial anatomy. I don’t think he ever published an analysis of its postcranial anatomy.


Southern Adventist University opens Origins Exhibit

David Read: Eddie, ecological zonation will yield the same basic order that you’re pointing to: invertebrates appear before vertebrates; fish appear before amphibians; amphibians appear before reptiles; reptiles appear before mammals; reptiles appear before birds, etc.

It could, and it’s the best creationist explanation, but it doesn’t explain why flowering plants were absent from lowland forests. Or why so many land plants appeared before mangroves, which today occur strictly in the intertidal zone. Or why no pre-flood humans have been found. Or, if Sean is correct that the flood ended at the K-T boundary, why many modern groups of birds and mammals (including marine mammals) which first appear during the Tertiary were not buried by the flood.

David Read: The fact that something appears before something else in the fossil record is not proof than anything evolved into anything else.

True.

David Read: You seem to be complaining that God has not made the fossil evidence compulsory, i.e., so clear that no reasonable person can possibly doubt it. And if God hasn’t made the evidence skeptic-proof, then the skeptic is God’s fault, God is responsible for the skeptic.

I’m not complaining. I’m merely pointing out that the evidence can be interpreted in different ways by honest people. And I’m relieved to see that even you don’t think the evidence is crystal clear.

David Read: Only people of faith can be saved, that is, only people who are willing to trust God and put away doubts can be saved.

I agree.


Southern Adventist University opens Origins Exhibit

David Read: Those tracks are so obviously bird tracks that the fact that some scientists want to assign them to “birdlike theropods” is itself a very useful teaching tool as to how the model creates the data.

David Read: That the model actually creates the data is one of the hardest concepts to get across, not only to lay people but even to the scientists themselves.

How does the model affect the data? Data don’t change and they shouldn’t change. It’s the interpretation, not the data, that is affected by the model.