This must be Thursday. I never could get the hang of Thursdays.
— Arthur Dent (Douglas Adams, The Hitchhiker’s Guide to the Galaxy)
Last Thursday, my wife gave birth to our second child. Nine months of prenatal vitamins, heartburn, lower back pain, kicking, and sleepless nights culminated in the delivery of a beautiful baby girl.
However, the process of delivery leaves much to be desired. For those who have never experienced mammalian reproduction, allow me to summarize it thus. (Warning: no storks, buns, birds, or bees are involved.)
- A sperm donated by the father delivers 50% of the future offspring’s genetic material to an egg from the mother, which provides the remaining 50% of the nuclear DNA.
- The fertilized egg cell begins to reproduce exponentially by mitosis, becoming a 16-cell blastocyst.
- The blastocyst implants itself in the wall of the mother’s uterus, and undergoes gastrulation, differentiating into three layers of cells.
- The embryo continues to develop by siphoning off nutrients from the mother through the placenta and umbilical cord. It continues to grow inside the mother, like a parasitic Xenomorph waiting to burst free of its victim.
- Skip ahead a bit. The cells have reproduced, differentiated, and embryological development has worked its magic to turn a tube of marginally differentiated cells into a full-fleged mammal fetus.
- Now here’s the tricky part: the developed fetus is delivered by the mother squeezing it out through the cervix.
Those last few steps are rather unpleasant. Particularly the last one. If there’s an intelligent designer, he must’ve been out to lunch when mammals were planned out.
So how do other species do things?
Fission, Budding, Cloning
No, not nuclear fission. There’s no plutonium involved here: it just means the organism splits in two. This happens mostly in unicellular organisms, and usually results in two identical offspring.
A cnidarian known as Hydra (the genus Hydra, not the mythological creature slain by Hercules) can reproduce by budding: buds grow on the body of the Hydra, which eventually grow into adults and break away from the original body.
This would be a strange way for humans to reproduce. One day, you might notice a bulge on your body that just kept getting bigger and more human-shaped as time went on. Eventually, that bulge would break away and continue living life as a grown human, your genetic twin.
Pando is a clonal colony of quaking aspen trees: many individuals covering a wide area, with a total weight greater than 6,000 tons, but all connected by a single root system. Many plants and fungi (and many other organisms) can form clonal colonies through underground roots, stems, or vines.
Unlike plants and fungi, human bodies don’t grow elaborate root systems or underground vines, so it’s hard to imagine humans reproducing this way. It would probably be much like budding.
Literally means “virgin birth”. A single individual fertilizes itself and bears young that are either full clones or half-clones of itself. This is a recurring motif, seen in isolated species across many phyla. It’s seen in rotifers, in insects, crustaceans, reptiles, etc. Oddly, it’s never been seen in a mammal.
In some species, parthenogenesis occurs when no suitable mates are available. In others, called obligate parthenogens, individuals reproduce exclusively in this manner.
If humans were parthenogens, we would be able to euphemistically knock ourselves up. This has only to do with fertilization, not the whole reproductive process, so we’d still be faced with all the messiness of childbirth. Still, this might make an interesting SF story.
Spores, Pollination, Egg-Laying
Ferns and some fungi reproduce by sporing. They produce hardy cells called spores that are scattered widely, and eventually grow into new organisms.
Pollination is also common in plants: a sperm and egg cell unite and… well, you know the rest.
Egg-laying is also quite common. The birds and the bees do it, so it’s strange that “the birds and the bees” are a euphemism for… well, you know. Even a few mammals lay eggs. Those are the monotremes, such as the platypus, and they are all native to Australia and New Guinea.
So why don’t humans lay eggs? It’s straightforward, it’s easy to establish a nest and provide warmth and safety for an egg, and it’s probably not nearly as painful as pushing out a baby. I’ve tried in vain to convince my wife that this would be a better method of reproduction.
As far as I know, this isn’t seen in nature, but it would be interesting to see a species specialized in such a way that young are assembled by a “factory” parent.
The evolutionary history of such a species would probably be very confused, but on the other hand, cnidaria such as jellyfish go through multiple and very different stages of life where individuals take the form of a medusan (jellyfish), a polyp, and free-floating unicellular creatures. And insect societies such as ants are highly structured with specialized individuals for different tasks within the colony.
I’d be interested in seeing a SF species that reproduces through a “factory” individual that assembles new individuals of the species. This is probably how intelligent robots would reproduce themselves. (Either that, or some sort of bizarre grey goo-style spore process.)
Humans should lay eggs. It would just be much less painful than the current method, and mothers wouldn’t have to deal with nine months of having strange octopus-like movements within themselves.