Zoological diversity

I just wanted to pick up on what Steve Hays astutely said:

Finally, suppose we ask ourselves what biology would look like if God wanted to create a world with maximal zoological diversity. That would mean you could arrange species along a continuum of similarity and dissimilarity. Some species would be more alike while others would be less alike. Some would occupy the extreme ends of greatest similarity and dissimilarity while others would represent gradations in-between. For any two species, they are either more alike or less alike. You'd have a nearly infinite range of fine-grained variations.

If so, then man is bound to resemble some species more than others, and there will be a few species he most closely resembles. But is that due to common descent, or is that just the inevitable result of God making a world in which he rings the changes on body plans?

If God wanted to make humans completely discontinuous with all other life on Earth, then he could have made our entire genome fundamentally different from all other life on Earth. Perhaps instead of DNA or RNA, God could have based it on something different like XNA. Or God could easily not even use nucleic acid or nucleotides at all. Perhaps he could have used XYZ, ABCXYZ, or whatever.

However, if God did this, then it's possible we would suffer various incompatibilities as a result. For example, perhaps consuming water, plants, and animals on Earth would not give us energy (ATP). Worse, maybe doing so would be toxic to us. Scifi often explores these sorts of things. A human astronaut travels to a distant planet orbiting a distant star, but finds he or she can't breathe in the alien atmosphere. An alien species (a plant or animal analogue) which is innocuous to other aliens in their system is introduced to humanity only to pose an imminent threat to our existence. And so on. Hence, presumably, God would need to make us compatible enough to other lifeforms on Earth so we can all co-exist, etc., but unique enough to reflect his special handiwork (imago Dei). If so, then there would be various degrees of compatibility as well as incompatibility with one another.

Moreover, if God did create us with fundamentally different genetics, I assume secular scientists (among others) would still find a way to argue we're not God's creation. Perhaps they'd argue we're aliens on Earth à la Crick's panspermia theory except applied only to humans rather than all life on Earth, which would be "proof" of extraterrestrial intelligence and civilization, which in turn would somehow evidence God did not exist. In any case, secularists would find a way to conclude heads they win, tails we lose - and "life"? It just happens.

Background to pop gen

Here's some quick and dirty background info for those curious about population genetics. It'll be simplified for wider popular appeal, but hopefully not overly simplified. I won't talk about population genetics itself, per se, since that'd be a bit too time-consuming for me to provide right now. But the background should provide enough knowledge to get people started on learning about population genetics on their own.

1. DNA. The first thing to know is that we're made up of DNA. DNA is a molecule that resides in us and encodes all our genetic information. We can think of it as containing all the instructions for how to make a human being.

2. Genes. DNA is composed of genes. Genes are segments of DNA that give humans form and/or function. Genes are also passed on from one parent to their child.

3. Allele. An allele is an alternative form of a gene. A variant. For example, different eye colors (e.g. blue, brown).

4. Genome. A person's genome is all the genetic info in a single person. This is all the DNA in a person.

Usually when we refer to DNA, we're talking about the DNA in a person's chromosomes aka chromosomal DNA. But there's also what's called mitochondrial DNA. That is, DNA in a person's mitochondria as well.

There are further distinctions but this should suffice for our purposes.

At any rate, a person's genome would include all the DNA.

5. Population. A population is all the organisms in a given set that can interbreed with one another. Actually, this is a very basic definition. It isn't perfect by any means, and debatable. But we'll just stick with this for now.

6. Evolution. A basic definition of evolution is a change in the frequencies of genes/alleles in a given population. Again, somewhat debatable, or at least requiring more elaboration, but we'll move on.

7. According to neo-Darwinian evolutionary theory, there are at least five factors that can influence the frequency of the genes/alleles in a population:

a. Natural selection. This is based on fitness. This is when the fitter or fittest individuals of a population survive (e.g. thick coated foxes are more fit to survive in the Arctic than thin coated foxes), pass on their genes/alleles, and thus their genes/alleles become more frequent in a population.

b. Sexual selection. This is based on sexual attractiveness. This is when the more sexually attractive individuals of a population mate and have the most offspring, thus passing on their genes/alleles, and thus their genes/alleles become more frequent in a population.

c. Gene migration. This is based on movement. This is when new individuals with new genes/alleles migrate into or out of another population, thus changing the frequency of genes/alleles in a population.

d. Genetic drift. This is based on chance. This is when random chance events (e.g. bugs getting stepped on, floods wiping out half the population) lead to changes in the frequency of genes/alleles in a population.

e. Mutations. This is based on anomalies in the genetic code. This is when mistakes in DNA lead to new genes/alleles.

7. Equilibrium. Specifically, Hardy-Weinberg equilibrium. A population is said to be in (Hardy-Weinberg) equilibrium when none of the previously mentioned factors are in operation. It also assumes all individuals in a given population capable of breeding are breeding and each produces the same number of offspring.

That is, natural selection is not at work. Sexual selection is completely random. There are no new migrants into or out of a population. There is a huge population size in order to moot random chance events affecting the frequency of genes/alleles in a population. Finally, no mutations ever occur.

8. Finally, as the cornerstone of population genetics, we have what's called the Hardy-Weinberg equation. The equation is: p² + 2pq + q² = 1.

We can think the equation in the following way.

Consider three basic types of genes/alleles. Say we have XX genes/alles representing dominant genes/alleles, xx representing recessive genes/alleles, and Xx representing mixed dominant and recessive genes/alleles.

Accordingly, the "p²" in the equation refers to what's called homozygous dominant genes/alleles. The "q²" refers to what's called homozygous recessive genes/alleles. And the "2pq" refers to what's called heterozygous genes/alleles.

If we know 40% of a given population posses homozygous dominant genes/alleles, then we know p² = 0.4.

If p² = 0.4, then p = 0.63 (approx).

That means q = 1 - 0.63 = 0.37.

While q² = 0.137.

And 2pq = 0.466.

Thus, since we know p² = 0.4, 2pq = 0.466, and q² = 0.137, then we know 40% of the population possesses homozygous dominant genes (e.g. XX), 46.6% of the population possesses heterozygous genes/alles (e.g. Xx), and 13.7% of the population possesses homozygous recessive genes/alleles.

DNA seen through the eyes of a coder

This is pretty cool.