Is Sex Necessary
Sex is part of our lives, and I feel a need to share this article I wrote some years ago. It is not more about why we should have sex, or even why we shouldn’t but rather whether sex is really a necessity in human or animal existence. Contrary to common belief, sex is not absolutely necessary for reproduction or continuation of living life to exist, infinitely. This post might bore many, those who are more interested in the mundane, readers whose writing deity is one “wanjohi wa Kigogoine.”But for those whose brains yearn for a little more informative knowledge, and do not shy away from knowledge as a vamp turns away from sun, read on. You might learn a thing or two, but even if you don’t, the courtesy will still be duly noted, and appreciated in equal measure.
Most organisms reproduce to a great extent without having sexual intercourse between the male and female members of the species. This phenomenon is called parthenogenesis, and involves production of offspring by female members of a species while they are still virgins. Parthenogenesis is quite common in many groups of animals and other organisms. It is only mammals and dragon flies that do not feature in this group of organisms that do not go through parthenogenesis.
The order Hymenoptera is uniformly parthenogenetic, because all males are born without any contribution from a male. This order includes bees, wasps and ants. He gives an example of an organism that has perfected parthenogenesis. This is the aphid. The aphid starts as a dormant egg rooted to the bark of a poplar tree. This egg sucks nutrients from the sap of the tree, and soon matures into a female aphid. It continues sucking the sap and it matures to puberty. On reaching puberty, the female becomes pregnant automatically and later gives birth to a colony of other wingless females. These females also suck sap from the poplar tree and later give birth to more wingless females. This cycle continues for three months until the tree can no longer support more aphids. At this point, the next generation of females is born with wings, and they fly off to search for another plant to colonize.
When they get a new plant to colonize, the cycle starts again. Generation upon generation of females is born without wings. Then, when the colonized plant can no longer support the colony, the next generation which is born has wings. This cycle continues for about six months, up to September, when healthy plants to colonize become hard to find. This group of females gives birth to a completely different type of offspring: winged males! Meanwhile, all the females born in this generation at the poplar tree have wings and know the meaning of sex. The males fly around looking for mates and the copulate with these females, who then lay eggs which attach themselves to the barks of the poplar tree sucking on its sap, and the cycle is completed. In this example, Quammen notes that these aphids are able to reproduce very rapidly and colonize unfamiliar habitats, while at the same time exploiting available resources. These are opportunists, and this is common among many insects.
In contrast, other organisms, such as vertebrates, are equilibrium species, and reproduce more slowly and maintain constant population sizes. We note that parthenogenetic organisms are opportunistic. Parthenogenesis, he argues, is quick and allows organisms to reproduce rapidly as long as food is available. It also ensures that offspring have the same genetic makeup as the parents, hence no tampering. The genetic pattern of the parent is passed to the offspring unaltered. However, this means that the lack of genetic changes makes them be unable to adapt to changes in habitat. In contrast, organisms which reproduce sexually mix the genes from both parents to make sure that their offspring has some traits that neither parent had. This might be more advantageous to the offspring for survival, he notes. Therefore, parthenogenetic organisms attain rapid reproduction rates at the expense of flexibility. This means that they find it very difficult or even impossible to adapt to changes in the ecology. They can only survive in a particular ecological niche.
Due to their inability to adapt to changing ecology; parthenogenetic organisms eventually become extinct or are forced to revert to sexuality to ensure propagation of their species. Therefore, we realize that sex is necessary, even if it is on an intermittent basis, for the propagation and adaptability of a species as seen in the case of aphids.