My first point is about the meaning of the word species. Species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. This means that you can't apply this concept to all forms of life, in other words, some forms of life can't bee classified as species in this way. The best example are the Prokaryotes. Surely they can be morphological classified, but not as species.
Secondly, you can't understand a species without understanding sexual reproduction. Today, sexual reproduction means processes that pass a combination of genetic material to offspring, resulting in increased genetic diversity. But this may be a bad definition, making the evolution of sexual reproduction a major puzzle. A bad definition, because Sexual Selection is in fact a very simple puzzle as I will show next.
The placed pieces of the classic view do not solve the puzzle, because they are wrongly positioned in the next way:
- Speciation (some organisms);
- Sexual selection (all species).
Now you can complete the puzzle in a extremely trivial way, knowing that sex is the mechanism that support speciation like the mammal womb discard the need of eggs!
For the question, why sexual reproduction? You may simple answer, because it's the mechanism of speciation.
In this moment some may ask, but aren't there asexual species? We should never forget that we are first of all working with words and their meaning. Words are some times very miss leading and more subject to opinions than facts.
For a child, a tree is an asexual organism, like for some grownups, because for them trees don't move. For a classic evolutionist a tree is a sexual organism, because its wisdom says to him that trees have sexual organs. However, they are all wrong!
Thinking in the Parthenogenesis, we may ask, are not they asexual species? Again, for the classic evolutionist, its wisdom says yes, they are, because they are all females. Here, the classic evolutionist it's like the child thinking in trees, arguing that they don't move!
The answer is in fact very easy, and lies in the first question. When we ask if there aren't asexual species, the answer is an absolute no, there are not asexual species, because sex is the de facto speciation mechanism. Thinking again, Parthenogenesis are species, so they are sexual. Simple isn't it?
No? OK, I understand! Let's return to the tree example. Trees are not sexual only because they have sexual organs, they are sexual because there is a process that can be classified as sexual selection. In this process we have more than the flowers, we have the pollinators. Pollinators are not only participants but essential to the sexual selection achievement. Now the child knows that albeit trees don't move, bees fly.
"If the bee disappeared off the surface of the globe then man would only have four years of life left. No more bees, no more pollination, no more plants, no more animals, no more man." - Albert EinsteinClassic evolutionists can't see Sexual Selection as a no matter what kind of process (mating courtship), unlike the anything matter kind of process of the Natural Selection (where the first works a priori, and the last a posteriori), and it's because that they need sexual organs, and it's because that they don't see bees, and it's because that Parthenogenesis are asexual, and because all of that, they say:
"A lack of sexual reproduction is relatively rare among multicellular organisms, for reasons that are not completely understood." - Wikipedia, Asexual reproductionThe no matter what kind of process in Parthenogenesis, for instance in the case of the New Mexico whiptail, makes that despite being an all female species, the whiptail still engages in "mock mating" with other members of its own species, giving rise to the common nickname "lesbian lizards". A common theory is that this behavior stimulates ovulation, as those who do not "mate" do not lay eggs. By other words, the classic evolutionist doesn't see the mating process as central in sexual reproduction, the classic evolutionist can't see beyond the organism's physical hardware, where instead, sex is all about software, all about species.
To be continued...
An Open Letter about Natural and Sexual Selection by Rui Monteiro - 2010