If you’re like most people, you don’t think much of turkeys until one appears tied up and roasted on your Thanksgiving table. Corn turkeys are interesting animals. The savages, great as they are, spend their nights perching in the trees. They have excellent vision and can see in color. You can tell their sex from their poo (male turkey droppings are J-shaped). One of their best tips, however, is that they are capable of parthenogenesis.
Parthenogenesis literally means “virgin birth,” but that has nothing to do with the common conception of virginity – birds that have already mated can do that too. Instead, it has everything to do with reproduction without sex. Parthenogenesis is the development of viable offspring from unfertilized eggs, no sperm is needed.
Thank you daddy, but mom has it covered
It occurs less frequently in complex organisms than in simple organisms – such as wasps, bees and ants – but parthenogenesis is not as rare as one might think.
Over 80 species of vertebrates reproduce asexually under certain circumstances and more and more are being discovered all the time. It is relatively common in fish, lizards, and snakes. the Sharks may remove it, too, on occasion. Turkeys aren’t even the only birds to do this, either. Pigeons, zebra finches, and some quails are all known to reproduce asexually.
Scientists from California Condor Recovery Program, studying the genetic diversity of bird DNA, were recently surprised to discover that two of the female birds had produced live chicks (in 2001 and 2009) without the help of a father. Both chicks died before reaching sexual maturity, but that was not surprising. When parthenogenesis occurs in birds, the young usually die before they hatch.
Why skip sex?
Sexual reproduction has an evolutionary advantage over asexual reproduction. The mixing and pairing of two sets of genes creates greater genetic diversity in the offspring, each of which inherits a unique combination of genes from its parents. This means that at least some individuals of the species are likely to have the traits necessary to survive if the environment changes, making it more likely that the population as a whole will resist those changes.
A population produced by single parents wouldn’t be as likely to have useful traits if climate change or a new predator or disease came to town. Yet in many situations being able to go it alone is a clear advantage for a species. On the one hand, it is effective. Organisms that reproduce asexually don’t have to take the time and risk to find a mate. Asexual reproduction is also faster and requires less energy. An animal that can reproduce without a partner can keep the species alive when it is in an area where there is no one to mate with.
Science does not fully understand why parthenogenesis occurs but, at least in birds, several factors seem to be able to trigger the process. Changes in food, temperature changes, and some viral infections have been shown to increase their incidence.
Lessons to learn
Humans cannot reproduce asexually, of course. No mammal can, to our knowledge.
Indeed, the reproduction of mammals involves what is called genomic imprinting: genes are marked or printed, depending on whether they come from the mother or the father. Some genes are turned on based on their original parent. This means that if all of a person’s genes were from the same parent, some crucial genes would remain turned off and they would be unable to survive.
But a better understanding of parthenogenesis could help advance research on assisted reproduction, the study of human reproductive disorders and how stem cells are produced. So on Thanksgiving, let’s thank the turkey for that.