Evolutionary ecologists have discovered that having sex with a male sea monkey from the future can be hazardous to a female sea monkey's health.
Nicolas Rode from the Centre for Functional and Evolutionary Ecology took advantage of sea monkeys' ability to weather droughts by remaining in their eggs for years before hatching once the water returns. He gathered eggs from layers of dirt formed in 1985, 1996 and 2007, and then reared them in their lab -- having females mate with males from their own time, as well as from other years.
The conclusion was disturbing. The further away in time the male sea monkey was from, the sooner his female sexual partner died. A male from 22 years away (about 160 generations) cut short the life of his baby-mother on average by 12 percent.
The reason is that male sea monkeys, like the males of many animal species, compete violently over who gets to mate with a particular female. The males evolve all kinds of weaponry to achieve this, from scoops to get rid of sperm from other males to the injection of "anti-aphrodisiacs" to stop the ladies having any desire to mate further.
That's not good news for the females. From an evolutionary perspective, the health of a single female is completely unimportant to a male, so long as they live long enough to birth another generation of offspring. As a result, some of the weaponry developed by the males can be downright toxic.
But the females fight back, evolving antidotes to the males' weaponry, which then force the males to evolve countermeasures, which in turn makes the females evolve more antidotes, culminating in an escalating arms race of sexual conflict, at least in theory.
Unfortunately the data from Rode's experiment wasn't clear-cut enough to determine whether that conflict does indeed escalate indefinitely or whether -- as some evolutionary ecologists suggest -- different sexual weaponry goes in and out of fashion over time, like an evolutionary merry-go-round.
Interestingly, too, is that the time-shifting didn't have any measurable impact on the sea monkeys' overall reproductive success -- the females dying early produced eggs at a faster rate to make up for it.
But either way, be warned: sex with time travellers appears to be far more dangerous than anyone had previously realised.