Vive la différence! – but how did it begin?

Did Darwin forget to ask how sexual reproduction evolved?
Dorothy Vining | Nov 24 2009 | comment  



We have published several articles this year to mark the 200th anniversary of the birth of Darwin, and the 150th anniversary of the publication of The Origin of the Species. MercatorNet has been presenting articles on both sides of the debate. Below, Dorothy Vining wonders if Darwin forgot to ask how sex evolved. Join the discussion on this topic on MercatorNet's Facebook group

In my twenties, I was responsible for indexing Darwin's works for the Great Books Syntopicon under the direction of the well-known philosopher Mortimer Adler. At the time I swallowed the Darwinian "natural selection" scenario hook, line, and sinker. It was so beautiful, so overarching, so all-explanatory. But later on I came to realize that too much was left unexplained.

One question that has baffled me is the origin of sexual reproduction. As far as I can see, this is an unsolved puzzle amongst scientists.

Apparently Darwin did not wonder about it. Either it has not occurred to his followers that they have no explanation for the beginning of sexual differentiation into male and female, or they are deliberately ignoring it.

Evolutionists point out that sexual differentiation has both costs and benefits. They point out that reproducing sexually is costly in that time and energy have to be devoted to finding a suitable partner. There is a risk of remaining unmated. There is a risk of producing offspring less fit than the parent because of recombination. Other things being equal, asexual reproduction is quicker and easier. Asexual reproduction is more common in species little troubled by disease.

On the other hand, sexual reproduction increases diversity and the likelihood of survival in changing circumstances. It purges the species of damaging mutations so that they can evolve new defenses against infections. Some animals actually breed sexually and asexually at different times!

But as to how sexual reproduction originated there is little said. In Why Have Sex? The Population Genetics of Sex and Recombination, (2006) Otto and Gerstein mention some of the reasons for sex listed in the previous paragraph. But they offer no answer as to how it all got started.

Confronted with the fact that sexual differentiation actually does exist in most multicellular animals, we have to surmise that at some point throughout the millenia one of these creatures in the process of cell division just happened to develop a cell with only half the usual complement of genetic material. We might call this a rudimentary egg (oocyte or ovum). Whatever could be the advantage of producing an egg? An egg would be of absolutely no use unless there was a sperm to fertilize it. If this animal found no mate, it would, of course, have been the first and last of its kind!

Well, perhaps another creature of the same species accidentally produced a sperm, complete with a tail. Why do you suppose it would grow a tail when it didn’t have a clue that it would have to go swimming after an egg? And of course it would not be genetically preprogrammed to recognize an egg if it should chance to run into one!

If we accept evolutionary theory we are required to imagine that each animal that today reproduces sexually, in the distant past was going about its business of reproducing asexually, dividing and budding away, when all of a sudden it accidentally produced an egg and at the same time, in the same locale, another animal of the same species just happened to make a sperm cell. Also, simultaneously and independently they each accidentally acquired the apparatus to get the egg and sperm together so they could produce offspring with a full set of genes.

Are you buying this?

If ever there was a case of "irreducible complexity", we have one in the transition from asexual to sexual reproduction. Irreducible complexity means simply that the process cannot be reduced to a series of simple steps one after another. If a number of things do not happen and come together all at once, nothing works. Irreducible complexity has been defined in various ways but I prefer Darwin's own language: "If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case" (Origin of Species, Chapter VI).

But as far as I can see, sexual differentiation is such a case.

Asexual reproduction results in progeny identical to the parent, unless there is a genetic mutation which will produce some change in the DNA. For an organism to initiate sexual reproduction additional genetic information is required, not only added to one organism but added simultaneously to two organisms of the same type, at the same time, and differing so that the changes will be complementary. There is no point in having a genetically female animal if there is no matching male anywhere around.

Accidental genetic mutations are almost always deleterious and have never been shown to involve an increase in genetic information. Consider that the informational content of the DNA in a single human cell equals that of 30 volumes of the Encyclopedia Brittanica. Where did all the new additional information required for sexual differentiation come from?

I have never seen any even remotely plausible explanation of how sexual differentiation might have first evolved in the Darwinian scheme of things. To my mind, the very fact of sexual differentiation necessitates, yes, demands a plan. And a plan demands a planner. "Male and female He created them," not "Male and female they decided to become."

Dorothy Vining once worked for the philosopher Mortimer Adler on the Syntopicon, an index to the ideas in the 54 volume set of The Great Books of the Western World. As her field was the biological sciences, she was assigned to index the biological works of Aristotle, Hippocrates, Harvey, Galen, and Charles Darwin’s Origin of the Species and The Descent of Man. An enthusiast then, she became increasingly critical of Darwin’s theories. She blogs at Musings at 85.

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