Sexy Endings


Never heard of the dasykaluta? The phascogale? Don’t be surprised. Small marsupials rarely get favorable media attention. Look at how we treat mice.

But these otherwise insubstantial, arthropod ingesting (that includes roaches) rodents deserve our interest and perhaps our piteous respect. For they show the lengths evolution can go to keep a species going. In this case, the wholesale obliteration of all males.

Immediately following frenzied sex.

The Problem

The insects that these small marsupials live on swarm and increase in number at very specific times of year. Your food source gets really plentiful, but only for a short short period of time.

The Solution

What are called “female led” evolutionary reproductive cycles. The mating season is brief. Sometimes, through the intervention of biological clocks, it consists of all of one specific day. For the whole year.

Reproduce that day or nothing. Talk about pressure.

And the females have the option during these marathon sessions of communal orgy to mate with any male they choose. Which they do, repeatedly.

The first result—massive sperm competition. Those most capable of getting there first and foremost get their genes reproduced. The rest will never see or know any offspring.

They won’t them anyway. At the end of the session, all the males die off.

Suicidal Reproduction

Semelparity is the term used to define reproduction followed by suicide. Though most of us might think the term was invented first for kinky science fiction novels or Marvel comic calendars, it’s a fairly common practice on earth. It is especially popular with fish. We just don’t think of it as happening to our fellow mammals.

But once the males have engaged in their biologically clocked, environmentally conditioned and evolutionarily prescribed mating frenzy, they drop dead.

How? It’s actually a bit complicated, but steroid levels—major stress hormonessurge to remarkably high states. Effectively, the brakes come off. Partially as a result, testosterone levels reach heights pop producers tend to call “off the charts.”

What’s the end result of superhigh steroid and testosterone levels? It's “immune collapse.” Reproduction over, the males just fall apart, experiencing a quick, collective end.

The females of course all stick around. Fatherhood is not an issue for these particular offspring. Parenting gets done by Mom.

Why Is Suicidal Reproduction So Effective?

The food supply is constrained. When it appears, so comes sex and reproduction—really fast. Everybody competes. And the competition is out in the open—literally. The females can get to know all the males they want, and be very unconcerned about what happens to them afterwards. The winners really win.

It’s the kind of scenario some entrepreneurial economists might find proper and just in specific human circumstances —except for twinges of regret from a few male commentators. But then again, human males may overrate sex. Plenty of species have the capacity to reproduce asexually—especially when there are famines around.

What Does This Say About Evolution?

Life on earth is extraordinarily varied and adaptive. What counts is that the species survives—anything thrown at it.

Individual don’t matter much. In many ways, they don’t matter at all.

What does matter is keeping diverse genes in the population.

What Does This Say About Stress?

Several things. That too many stress hormones can kill you—sometimes rapidly. In human examples, twenty five year olds left without food alone at sea may experience heart attacks and watch their hair turn white—overnight. Pushing the pedal and reaching for extremes may work for us on the species level, but it’s hell on individuals.

Second, it’s obvious that for some mammals there can be a thing as too much testosterone.

The human story of testosterone is quite different. But fans of the multibillion dollar testosterone “replacement market” should take note.

We don’t know the long term effect of all those extra sex hormones. And we certainly must look at single hormones in wider context. It’s become pretty obvious over the last few years that looking at testosterone levels in humans—without considering estrogen, often produced from testosterone—is like trying to understand a language with its vowels stripped out.

These are complicated systems. How they interact is what counts. As to how most of all that really works, we only have a couple of clues.

Pity the Poor Mammals

Biology is inevitably highly inventive. Life on earth is violent, nasty, brutish and short. Getting the best genes to survive unknown adversities may explain the importance we ascribe to human sex. That’s particularly true when we look at “sexiness” —and why the bad girls and bad boys are so attractive.

Sex and death—they really do go together.

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