Does that sound like the name of a hardcore metal grrrl band to anyone else? No? Well, when I tell you that there are multiple species of lizard in Mexico and the US Southwest that are all female and that no male members of these species exist, I am not kidding (nor am I writing a science fiction novel). It’s a real thing, kids. A species of animal that needs only one sex to reproduce is called parthenogenetic, and surprisingly, it happens in over 70 species of vertebrates. Some species of snail, some pythons, hammerhead sharks and Komodo dragons are parthenogenetic (or will occasionally revert to parthenogenesis, depending on the circumstances). Also, just as a fun fact, the name itself comes from the Greek words parthenos or “virgin” and genesis or “creation”.
Parthenogenesis usually evolves in species that are extremely isolated–from other groups of similar organisms, from members of the opposite sex, or both. These lizards, hanging out in the baking deserts on the border between North and South America, fit the bill. Until recently, scientists were stumped as to how these lizards could produce fully formed offspring: in ‘normal’ sexual reproduction, the female contributes half the chromosomes in her egg while the male donates the other half through his sperm, and the two mix in different creative ways to generate genetic diversity within the population (not that DNA can get ‘creative’ per se, but you get my drift). So if there are no males involved in this process, how are the offspring getting the full complement of genes? As it turns out, the mother provides both sets of chromosomes all on her own.
These resourceful mamas start out the reproductive process with eggs that have twice the number of chromosomes as sexually reproducing females, meaning their offspring will be genetically identical, excluding the random mutation that is bound to occur. They also undergo some pretty fab-tastic genetic recombination with sister chromosomes to make sure the genes stay heterozygous. Although their method of reproduction can decrease the genetic diversity of the population and thus make the individuals more susceptible to disease and predation, it also means that a single lizard could explore and inhabit a new territory and populate it all on her own! (Think about how handy this would be if you were the only woman standing after the zombie apocalypse…)
Even though these lady lizards do not need a male partner to fertilize their eggs, (got it covered, bro, thanks!) they still need to engage in a copulatory act. This means that two female lizards, even though neither can (or needs to) fertilize the other, will perform the movements of traditional copulation. This sends the trigger to their brains that allows them to lay their eggs. The fact that mamas still need faux-copulation as a mechanism to signal egg-laying indicates that males were once an essential part of the species, and though the male population has been lost, the copulation trigger has been conserved as what animal behaviorists call a ‘fixed action pattern’ within the species. (below, two lady lizards helping each other out).
The BBC, as always, has some pretty awesome videos on the subject of parthenogenesis, as well as some commentary on the whiptail lizards themselves, so check it out! Revel in the fact that there are species on Earth that will produce countless virgin births in the years to come–someone tell the Pope.