Known as 'polyandry' among scientists, the phenomenon of females having multiple mates is shared across most animal species, from insects to mammals. This study suggests that polyandry reduces the risk of populations becoming extinct because of all-female broods being born. This can sometimes occur as a result of a sex-ratio distortion (SR) chromosome, which results in all of the Y chromosome 'male' sperm being killed before fertilisation. The all-female offspring will carry the SR chromosome, which will be passed on to their sons in turn resulting in more all-female broods. Eventually there will be no males and the population will die out.
For this study, the scientists worked with the fruitfly Drosophila pseudoobscura. They gave some populations the opportunity to mate naturally, meaning that the females had multiple partners. The others were restricted to having one mate each. They bred several generations of these populations, so they could see how each fared over time.
Over fifteen generations, five of the twelve populations that had been monogamous became extinct as a result of males dying out. The SR chromosome was far less prevalent in the populations in which females had the opportunity to have multiple mates and none of these populations became extinct.
The study shows how having multiple mates can suppress the spread of the SR chromosome, making all-female broods a rarity. This is because males that carry the SR chromosome produce only half as many sperm as normal males. When a female mates with multiple males, their sperm will compete to fertilise her eggs. The few sperm produced by males carrying the SR chromosome are out-competed by the sperm from normal males, and the SR chromosome cannot spread.
thinkahol * on 29 Dec 10For teenagers, friends play a big role in the decision to take that first drink. And by the 12th grade, more than 65 percent of teens have at least experimented with alcohol. But what parents do during the high school years can also influence whether teens go on to binge drink or abuse alcohol. Researchers at Brigham Young University have found that teenagers who grow up with parents who are either too strict or too indulgent tend to binge drink more than their peers.
Beatriz Arias on 14 Jul 11For some adults, there is a tendency to go beyond the call of duty. Particularly, when they are faced with choosing to allow or not allow. Maybe the scientific explanation is to do or not to do. And the reaction isn't always the most appropriate but it is better to be safe than sorry. What is the scientific explanation for adults that don't react or react inappropriately even when it's involves saving a teenager? What is the scientific solution for those in the center of difficult situations, who are not strict or liberal? What does a mind do when it is present many times in a teenage situation and it is not the parent?
