What you have is often not what you want. And this applies not only to human pairs. A new study made on several animal species found that when animals must mate with less-than-preferred partners, females and males apparently try to compensate that by increasing the chance of their offspring survival.

The research supports the Compensation Hypothesis, which explains how individuals transmit their genes even under non-ideal conditions.

"It's always better for offspring if parents can mate with preferred partners, but it's becoming clear that when parents can't have that preferred partner, they have ways of making up for it. When female 'choosers' were in enforced pairs with males they did not prefer, they laid more eggs. Similarly, when males are paired with females they do not prefer, they ejaculate more sperm. This compensation seems to be a way of making the best of a bad job," said lead author Patricia Adair Gowaty, a Professor of Ecology and Genetics at the University of Georgia.

The research was made on Tanzanian cockroaches, fruit flies, pipefish, wild mallards and feral house mice. In tests, when animals were impeded from freely choosing their preferred mates, they used methods meant to increase the survival chances of their offspring.

"Just how an individual finds its best mate isn't really known, though there's some evidence that he or she may be somehow sensing the advantage of the potential mate's immune system in relation to the chooser's own. Many factors are probably at work, including behavioral cues and what potential resources a mate may bring." said Gowaty.

Offspring were advantaged, but for individuals the benefits were none. Females mating with non-preferred males live less than those paired with their choice partner.

Compensation comes with a surprising turn to the theory of the natural selection.

"The study suggests that the best way to keep species alive may be, if possible, to let individuals choose their own mates," said Gowaty.

She has been working on the Compensation Hypothesis for over 10 years and published the first results only four years ago.
The hypothesis could also work in humans, but investigating the subject is practically (and ethically) improbable. Still, popular culture lays stress on it.