Contained within an unnessarily complicated article regarding the evolution of the Y Chromosome (which is actually quite fascinating but full of sentences written with Gregor Mendel in mind and not a layperson — it’s all DNA this, X Chromosome that, reinvigoration, chromosomal palindromes, blah blah blah), is this little nugget:
Sperm competition may have been important in the earliest humans, too, for some years after the chimp and human lineages split. Sperm competition could still play a role in human reproduction, some experts think, given the trickle of cases of heteropaternity, the birth of twins with different fathers.
Wait, what? Turns out there is such a thing as heteropaternity. In science terms, heteropaternal superfecundation, is “different fathers, multiple babies” through one pregnancy. It rarely occurrs amongst humans because of 1:1 coupling, but this genetic feat is quite common amongst dogs, cats and even chimpanzes.
For this to happen in humans, a women must engage in intercourse with two different partners in close proximity to one another within the same ovulatory period; in the strictest math terms sperm cells can live inside a woman’s fallopian tube for 4–5 days, while her fertility window is usually open for 5-7 days. This phenomena often goes unrecognized unless, for some reason, a DNA test is sought by the identified father.
I feel like a knowledge bomb just got detonated on my face.
Links to individual cases:
– MSNBC article about the Stuart twins
– Description of the Archer case at Straight Dope
– Case of a Croatian woman in 2003 at Flatrock.org
– Descriptions and references of a set of cases at ISRAelect.com (references unverified)