This shark just spent years alone and then, spontaneously, produced children.
Sometimes I think my Mom wishes I was this shark.
Howdy Sharky the shark dog and other fans, Trace here for DNews.
Leonie the zebra shark has been alone since 2013, when her partner shark was moved to
another tank.
Over the intervening years, she took up knitting, mixology, kickboxing, and spin and barre classes.
Finally, over a bottomless brunch with her gal pals, she decided it was time to chum
the water and download Bumble.
Wait no, that’s just my friend, and all that sounds completely normal and awesome.
Leonie did something strange, she was alone for four years, and then birthed a litter
of sharks -- a virgin birth!
And they have no idea how she did it!
In a new paper in Scientific Reports, scientists documented parthenogenesis in a zebra shark
that had previously had pups with a partner!
This was the first time they'd seen this animal switch from sexual reproduction to parthenogenesis!
Parthenogenesis, is asexual reproduction for higher life, and it’s been observed in plants
and invertebrates, but also some species of bony fish, snakes, lizards, rays, chickens
and turkeys!
And of course, sharks.
But what about us?
Could we just give up the other sex and go all asexual?
Parthenogenetic animals have some mutation that allows them to reproduce without input
of genes from another individual.
That addition of new genes is super important, because it adds genetic diversity, a.k.a.
Sex makes the gene pool larger.
Humans require 46 chromosomes -- or packets of DNA.
Mom and Dad each have 23 -- combined, the genetic information inside the chromosomes
create the plans for a full human.
So, yes, you could take two eggs (or two sperm) and mush them together and get that total
of 46, but there’s a problem -- genomic imprinting.
Unlike parthenogenetic animals, in mammals, bits of DNA are present in both egg and sperm,
but not all the genes are switched on.
Even if somehow two eggs merged into a zygote, the zygote wouldn’t make it far before finding
it was missing some genes it could only get from sperm.
Mom genes just don’t cover all the bits.
Thanks to genomic imprinting, sometimes the MALE version of the gene is used, and sometimes
it’s the FEMALE version.
One study in Nature Genetics, says we use 58 percent from pops.
Not to mention the Y-Chromosome… which makes fetuses male.
Don’t feel bad though, ladies, we can’t just use the genetics in sperm alone either,
because all mitochondrial DNA -- which keeps our cells alive -- comes from the Mother.
We’ve never had scientific proof of human parthenogenesis, though there have been multiple
claims.
In the 1950s, a paper in The Lancetdetailed the examination of 19 Moms who claimed virgin
birth.
They didn’t have DNA tests, so they looked at gene expression.
For example: Mom has brown eyes, kid has blue eyes?
There’s a Dad in the picture.= because recessive genes would only express if there were two
parents.
Part of the reason we’ve never had proof?
It might not be possible.
Genomic imprinting alone affects, scientists think, 200 different genes.
There haven’t been enough humans on our planet to see even one example of this happening
randomly.
And thanks to the number of genes, scientists don’t think this could happen naturally.
In a laboratory, with the right techniques, scientists might be able to create a “virgin
birth” but they’d still need genetics from more than one person.
So, if you were hoping to Forever Alone with your own little parthenogenetic kid; you’re
kind of out of luck.
Parthenogenesis, even in nature, seems like it would be completely impossible!
Don’t we all need that genetic variety?
If a Mom produces an exact copy of herself in the womb, isn’t that just a clone…
A study in Nature from 2010 finally figured out exactly how an animal could reproduce
with an all-female population and still maintain genetic diversity, and avoid debilitating
mutations…
They specifically looked at the whiptail lizard, which start with a ton of genetic diversity
to begin with!
Whiptail lizard eggs contain twice the number of chromosomes of sexual lizards of a similar
species.
So, when they start parthenogenesis, their genes don’t overlap, because they have so
much more to work with!
How did this evolve?
They’re… still working that out.
Even though sex in nature is fun (and messy and crazy and often weird) there are advantages
to being able to parthenogenetically reproduce -- populating a new area, for example, or
in the case of disease, or disaster -- the species goes on!
There are reasons that we have sex.
Lots of them.
You want to know more, of course you do, so watch this video.
Would you rather reproduce asexually?
Let us know in the comments, please subscribe for more DNews and come find me over on Twitter.
You can find me @tracedominguez and you find the show @seeker.