Why Do We Need Sex?  Ever Wonder?

By Shlomo  Maital   

 Woody Allen

  One of my favorite BBC programs is Discovery.  This week, Discovery is tackling a great question:  Why do we need sex?  Why did Nature invent sex?  Plants and animals can reproduce without it.  Hermaphrodites are both male and female (common in fish, jellyfish, and some flowering plants).   So why did Nature invent male and female sexes, that copulate to reproduce?  Ever wonder?  Nature is always efficient.  If it can reproduce with just one,  why require two?  Nature can reproduce itself through parthenogenesis (a form of asexual reproduction in which growth and development of embryos occur without fertilization).    Why two cells (sperm and egg) to produce one?   (OK –I know,  three cheers for sex and for Nature…but we can still ask).   Woody Allen once spoke about having sex with someone he loves – himself.  Why two?

    Biologists have shown that there are species which are capable of both asexual and sexual reproduction. These species time their sexual reproduction with periods of environmental uncertainty, and reproduce asexually when conditions are more favourable. The important point is that these species are observed to reproduce sexually when they could choose not to, implying that there is a selective advantage to sexual reproduction.  (Or, simply because it’s fun?  No – unacceptable answer. Evolution doesn’t select on ‘fun’. Nature doesn’t party.)

    Humans are close to parthenogenesis.  “On June 26, 2007, International Stem Cell Corporation (ISCC), a California-based stem cell research company, announced that their lead scientist, Dr. Elena Revazova, and her research team were the first to intentionally create human stem cells from unfertilized human eggs using parthenogenesis. The process may offer a way for creating stem cells that are genetically matched to a particular woman for the treatment of degenerative diseases that might affect her.”

    Here is a partial answer to the riddle, why do we need sex?

  “A sexual cycle is maintained because it improves the quality of progeny (fitness), despite reducing the overall number of offspring (the two-fold cost of sex). In order for sex to be evolutionarily advantageous, it must be associated with a significant increase in the fitness of offspring. One of the most widely accepted explanations for the advantage of sex lies in the creation of genetic variation.   Sex creates new gene combinations that may be more fit than previously existing ones,”

     What worries me is, biologists may through cloning eliminate the need for sex.  As several science fiction books recount, sex could then be banned as inefficient.  Take comfort – if a referendum were held on banning sex, it would be defeated, even in California.