Are virgin births really so special?
Few zoological phenomena have, over the centuries, aroused such strong interest in the general public as virgin births. Waterfleas and stick insects do it habitually; some aphids and flies will do it under certain favourable conditions, a few species of fish and even some lizards are known to be able to do it: to reproduce without males that is. These organisms are uni-sexual and produce offspring “parthenogenetically” as the scientist calls it.
While in lower organisms parthenogenesis (= virgin birth) occurs to varying degrees, it becomes increasingly rare the higher up the evolutionary ladder one climbs. Heat shocks, radiation, pin pricks, and electrical stimuli have all been used to trigger development of unfertilized eggs of frogs and newts and fowl-pox virus in turkeys is known to be responsible for the very occasional development of unfertilized bird eggs. Of 8,500 eggs laid by virgin hens, only four chicks developed spontaneously. If that can happen in birds, the question arises of course, couldn’t that happen in mammals, maybe even humans, as well?
Unfertilized egg cells of mice can be made to divide and grow into a maximally six day old embryo, but then the development becomes haywire and turns into a tumorous growth. In honey bees, where sex determination is very different from that of mammals, unfertilized eggs laid by the queen bee develop into haploid drones, which possess only half of the number of chromosomes that female bees, i.e. all the worker bees, have. Because in mammals sex determination is different from that of bees, females do not possess the male-determining y-chromosome and, consequently, any individual of virgin birth origin can, of course, only be a female. As to the possibility of a virgin birth in a human being, scientists agree that for now at least, it would be a miracle (and it would result in only another female unless there is an even greater miracle).
The biological advantage of parthenogenesis under certain conditions is obvious. Take for instance a single female aphid, blown by a gust of wind onto a suitable host plant. If it were to wait for the chance arrival of a male to mate with, the food source might have wilted and be no longer available to its offspring. So, why wait for a male if reproduction and population increase can proceed without the male contribution? The female waterflea, finding itself amidst the spring bloom of a most nutritious algal soup, is in the same predicament: either wait for a male or forget about sex and go about producing daughters that could make use of the resource as long as it lasts. Thus, parthenogenesis is the reason why in only a few days aphids and waterflea populations can increase to staggeringly high numbers. As for the human species, thank goodness we need not make such profound decision on whether to reproduce parthenogenetically or not: we are doing quite well without the need of virgin births, given there are now close to 8,000 millions of us on Earth.
© Dr V.B. Meyer-Rochow and http://www.bioforthebiobuff.wordpress.com, 2016.
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