Monday, July 7, 2014

Common Creationist Complaint: How did sex originate?

Common Complaint: How did sex originate? Asexual reproduction gives up to twice as much reproductive success (‘fitness’) for the same resources as sexual reproduction, so how could the latter ever gain enough advantage to be selected? And how could mere physics and chemistry invent the complementary apparatuses needed at the same time (non-intelligent processes cannot plan for future coordination of male and female organs). [1]

Answer: Sexual reproduction is incredibly advantageous, and it has to do with variation. Sexual reproduction creates variation whereas asexual creates clones. You don’t look exactly like your parents; you are a mix of both of them. You also don’t look exactly like your siblings even though you all came from the same genetic material. This “mix” results in different DNA from each parent and results in an almost infinite number of combinations. This allows for variation, and variation is very important to evolution. “Reproduction” may occur faster with asexual organisms, but “evolution” and the ability for a population to adapt to change occurs much faster with sexual organisms.

So let’s say you have two populations: one reproduces through asexual reproduction, the other through sexual. The asexual population would be identical to each other whereas the sexual one would be different. In our scenario, both populations become infected with the same disease. The cloned population would likely all die out because they would all be identically vulnerable to it. However, the variable population would differ in their vulnerability, and the odds are that there are at least some individuals that are resistant and would survive.

Sexual reproduction is adaptive because it creates variation, and  variation allows the population to adjust to environmental changes. There is a reason that the vast majority of life on earth reproduces sexually. It is necessary to accommodate to our ever-changing environment.

Now, as for sex organs, I have a simple metaphor for you: Lock and Key. But to understand why that’s important, we have to back up a bit.

As beneficial as sexual reproduction is, it’s expensive: time and energy to find and attract a mate, fertilization, pregnancy for those that do gestate, lactation.

Species are defined on their ability to produce viable offspring with each other. So if you mate with someone who won’t produce offspring that will survive, then you are wasting your time and energy. And that’s what survival is all about – efficient allocation of resources.

So you want to make sure that when you choose to mate, you are mating with someone who can help pass on your genes – a member of your own species.

Identifying members of your own species may be harder than you think, especially if the speciation event has been recent. Let’s say you have two populations of rabbits who were separated- fire, flood, earthquake. For a long period of time, the two populations didn't interact because there were no resources they would use connecting them. So there was no genetic exchange between the two populations. Now, we already know that genetic mutations occur very frequently – in humans, at least 100 times per kid. Rabbits reproduce rapidly, and with an average 100 mutations each offspring, it wouldn't take long before the populations became so genetically different that the chromosomes wouldn't line up right and the offspring wouldn't be “viable” - they would miscarry or the offspring would be infertile. However, the rabbits still “look” similar enough so that they might try to mate with each other. So there becomes this positive selective pressure to help to guarantee that only those who can produce offspring together do produce mate. And this can happen a variety of ways – behavior is one: specialized bird calls, mating dances; physical appearance is another: coloring and body shape - but one of the most sure-fire way to avoid mating with someone who is not of your own species has to do with the actual mechanics - a lock and key, for example. A key may look like it’s the right key, but if it doesn't fit, it’s not going to work. So all the different sexual organs for all the different species have evolved to help us make sure that we are mating only with those that “match"; individuals who mate only with other members of their species are going to have more reproductive success, and thus these behaviors and physical characteristics will propagate in future generations. Reproduction is the point of existence in life – again, another theme that, for me, just testifies that evolution is part of God’s plan on the importance of family – and if you are not using energy well enough to reproduce effectively, then you are not as fit as another one who does.

[1] 15 Questions for Evolutionists. Evolution: the naturalistic origin of life and its diversity (The General Theory of Evolution, as defined by the prominent past evolutionist Kerkut; see introduction to Origin of life.) by Don Batten

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