Here is a response I made to Steve, a christian posting on DC, to a popular myth about evolution spread by the likes of Kent Hovind.

OK, Steve has used the :

We all know that dogs give birth to dogs, not zebras, and ants lay eggs that hatch into ants, not Canada Geese.

approach, which is straight from the book of Hovind.

Firstly, let me remind you of a post I made here at DC about a year ago about there being no such thing as a species (objectively) -

Recently, I have been thinking about evolution. Not unusual for me. Many apologists attack evolution, and attack the notion that species can evolve into new species, and that there is no transitional fossil evidence for X,Y and Z. However, what they do not realise is that there is no such thing as a species. Objectively, such an idea does not exist.

'Species' is a label that we humans have attached to groups of organisms that we see common characteristics between. We also tend to attach arbitrary rules to them to, such as they cannot interbreed with another species, otherwise they are effectively the same species etc. What this labelling does is give a false impression that a) species are static; and b) that these labels define these organisms whether humans exist or not. These labels are human constructs - that is all. Every organism is constantly shifting its genetic blueprint. We are constantly evolving. Humans now are different genetically from humans 1,000, 5,000, 10,000 and 100,000 years ago. Yet we still define ourselves as the same species.

Species is a temporal notion. It is like taking a picture of all organisms at a given time and sorting them according to effectively arbitrary characteristics. There is nothing to say you can't sort species by the number of legs. On the temporal front, every organism (and I mean that in its entirety - every organism on earth at a given time) is shifting in evolutionary terms. There is a dynamism to evolution, though some organisms do it on a much faster basis than others.

It renders the notion of when a reptile became a bird, or similar claims, utter nonsense. The slow and gradual process of changing one's genome piece by piece to morph into something ever so different at each mutation is a paradigm shift away from a simple view of biological taxonomy.

Every organism sits on a continuum of evolution from the very first organism to what will be the last in the heat death of the universe. You can pick any organism alive today and follow its path back to the first in a linear fashion. By declaring that species exist (in a sort of objective, definite manner), all you are doing is chopping up that line arbitrarily.

Thus, species don't exist other than in the human mind. A perfect example, if you will, of philosophical conceptualism.

What Steve Hovind is saying is this: We don’t see dogs give birth to zebras, so evolution is false. Anyone with even the remotest idea of evolution knows that this sentence is ridiculous. Evolutionary biologists would never say this. Zebras would have to be on the same branch of the tree of life, coming evolutionarily further down the branch than dogs.

The above quote should allow you to realise the issues with this. But let me elucidate further:

What Steve would better be saying (and what Hovind actually says) is that dogs never give birth to non-dogs. In humans, we have about 3 billion base pairs in our genome with the number of mutations estimated at about ~3× or ~2.7×10−5 per base per 20 year generation.

Let’s say, for sake of argument, that dogs have about 60 mutations per generation and a 2 year generation, then over, say, 100,000 years there would be 50,000 generations making about 300,000 mutations. Then of course, there is breeding between subspecies which would cause much larger changes in the genome than mutation. There are also other types of evolutionary mechanisms.

Let’s imagine an early dog. Lets call it Dog + 0. So if we take Dog + 0 and compare it genomically to Dog + 50,000 you can see there would be a observable difference. It could be that Dog + 0 is actually a grey wolf and that dog + 50,000 is a Chihuahua, for example.

Now, the wolf would never give birth to a Chihuahua and a genetic biologist would be the first to say this. What Steve Hovind does is build a straw man. These subspecies are clearly distinct, though with a little help could probably still mate. However, further evolution would leave such a subspecies (say Dog + 100,000) unable to mate with the grey wolf.(Dog + 0), in all probability.

Either way, a dog does give birth to a dog (if we accept and arbitrary human constructed labelling system). But eventually, such a subspecies will become distinct from the original subspecies so one is left wondering whether it is, indeed, a dog in comparison to the ‘oringal’ (which is itself arbitrarily selected by a human out of a continuous. This will be more obvious if there remained a geographically, and thus genetically, isolated original dog (such as the wolf). But if all subspecies mutated and interbred etc, there would be nothing extant with which to compare such a newly evolved organism to. If I have made nay error with my claims here, please let me know. I am no evolutionary biologist myself, though I am at least willing to investigate what it all means and how it works. For MaryLouiseC, notice what it means by ‘how something works’. I don’t just assert THAT IT WORKS, but have a working understanding of the mechanism.

Basically, Steve, don’t make really, really naïve assertions about a subject with which you seem to have little expertise.