A friend of mine recently confessed to me that he preferred to think of himself as a virgin birth.  When I asked why, he said he likes to think that his parents never had sex.  I have no idea where he thinks he got his Y chromosome from, as his mother has only the two Xs, but I suppose invoking miracles to do away with inconvenient thoughts is hardly something he invented.  Much like industrial meat production and the effectiveness of sneeze guards at salad bars, the topic of parental sex is one item we would probably rather leave unexamined.

Some organisms don’t need to avoid this topic, as they can dispense with the sexual partner altogether and simply go it alone.  Being asexual makes things easy: no need for a bottle of wine, wooing, low candle light and mood music, but it is risky to just make perfect copies of yourself.  If you have the unfortunate habit of dying in response to a particular strain of flu, then living in a city filled with clones will really be a hit to neighborhood property values if that virus comes to town.  As a result, many animals spend a great deal of time trying to get their eggs fertilized by suitable sperm in an effort to see their genes for red hair and family history of alcoholism, represented in the next-generation.

Studies of sperm and eggs were all the rage in the late 18th century.  For example, the Italian priest Lazzaro Spallanzani found that by isolating frog eggs from females and ejaculate from males the two substances could be recombined in a test tube, and he could then recapitulate every stage of frog development. While this made Spallanzani the first person to ever carry out in vitro fertilization it also gave him the reputation of being “the underwear priest.” To collect ejaculate for males he had made small trousers out of pigs bladder to collect the requisite frog sperm.  He also performed the first artificial insemination of a mammal by taking semen “spontaneously” elicited from a male dog which was then injected into the vagina of a female poodle. Some 62 days later a small litter of pups arrived arguing that injection of semen alone was sufficient to fertilize a female dog’s ovum.

While these feats of scientific conquest undoubtedly made him a huge hit at Italian cocktail parties, when Spallanzani was not busy making undergarments for amphibians or trying to elicit dog semen, he was trying to better understand how fertilization worked on a fundamental level.  Unfortunately he and his contemporary, the Calvinist priest Charles Bonnet, became convinced that semen really just stimulated the development of a small preformed human, called a homunculus, that existed inside the ovum.  Such ideas of preformation were common in 17th and 18th century, with gentlemen such as Nicolaas Hartsoeker claiming to have seen similar homunculi within a spermatozoon back in 1694.  Bonnet and Spallanzani, were instead ovists, proposing that the “little worms” we know today as spermatozoa were parasites and do not as Hartsoeker proposed have anything to do with fertilization.

Hartsoeker’s drawings of the preformed humans that lived within his active imagination.

In retrospect these arguments can seem quaint, but it’s important to keep in mind that microscopes were not very good. As resolution got better, it became clear that embryos did not look very much like preformed humans. Given what Spallanzani and Bonnet knew at the time, they could have been excused for thinking that a single ovum was all that was necessary and that sperm was dispensable.  Bonnet had actually seen eggs develop in the absence of sperm, in the process we now know as parthenogenesis.  Bonnet had established the mechanisms of parthenogenesis in aphids.  These insects can undergo a switch from sexual to asexual lifestyle based on season. This virgin birth helps aphids reproduce quickly, decimating your garden in the good times (for the aphids), while switching to sexual reproduction before winter to help preserve genetic diversity during this uncertain transition and ensure at least some survive.

This mode of asexual reproduction is not only limited to aphids.  For example, 50% of Beltsville Small White turkeys, exhibit parthenogenesis and the whiptail lizard (Cnemidophorus uniparens) is famous in certain biological circles for their pseudosexual courtship behavior that persists despite the species lack of males.  This development of unfertilized eggs can even be induced in mammals.  For example in 1936 the Harvard researcher Gregory Pincus, managed to get rabbit embryos to develop using just ovum and manipulating the environment in a test tube, and then implanting the eggs into surrogate females.  This produced viable offspring which is quite the feat for the 1930s. Piggybacking off of this work a team in 2004 was able to show that with some genetic manipulation, and 460 attempts, they were able to get one adult female mouse, no sperm required.  This work aside, mammals are not generally thought to undergo parthenogenesis naturally, without these kind of herculean interventions.

This does not stop some mammals, of a human variety, from thinking they are going to be an exception to the rule. Humans tend to like to think that they are special. For example a study back in 2013 in the British Medical Journal found that in a sample of some 5,340 pregnant British women some 45 or just shy of 1%, claimed to be having a “virgin pregnancy.”  Four possibilities come to mind as explanations for this phenomenon:

1. Parthenogenesis occurs way more frequently than previously recognized
2. They may not be telling the whole truth about their sexual history
3. These study participants are woefully misinformed on the finer points of reproduction
4. Some British women just really enjoy trolling biomedical researchers

Regardless, this phenomenon is far from recent and virgin birth claims do crop up from time-to-time.  For example in 1955, Helen Spurway brought up the possibility that parthenogenesis in humans was at least theoretically possible, the British tabloid the Sunday Pictorial decided to go searching for these virgin births. Some 19 people came forward and a rather odd little study was eventually submitted to The Lancet in 1956.  Eleven of the nineteen needed to be eliminated because “They were under the impression that a hymen which remained intact after conception had occurred, was what was meant by a ‘virgin birth.’” This raises the question in my mind, how many claimed virgin births can be explained by this little mental loophole?

In any event, after some further winnowing based on criteria like blood type and some rudimentary blood tests, they are left with just one good candidate: Ms. Alpha and her daughter.  It’s at this point we are left at the mercy of the limitations of the technology of the time.  This is before modern DNA technology which would have made this claim easy to test, instead the researcher’s follow it up by seeing if skin grafts from mother-to-child and child-to-mother take hold.  You might expect these to take if they are in fact genetically identical.  The grafts were rejected, arguing that this case is not an example of immaculate conception, but the author decided he didn’t like the graft result and instead went with the tried and true interpretation of “you can’t prove it’s not parthenogenesis” and “let’s leave this for a future study that I will not be doing.”  To the best of my knowledge nobody has ever followed this story up, though my suspicion is that this is not an example of parthenogenesis but rather tabloid sensationalism.

At the end of the day, unless you are product of in vitro fertilization, your parents almost definitely had sex and you know what, that’s ok.  Sex is a wonderful and fulfilling part of life, and pretending it doesn’t exist just seeks to stigmatize it. Of course if you’re asked on a questionnaire if you are a product of “virgin birth” then definitely check yes. Nothing is more fun than messing with a group of virgin birth researchers.

Here for the sex, drugs, and rock and roll? Since we’ve just covered sex, come read more about LSD in My elephant’s drug dealer. Rock and roll will have to wait for later.