Why some rodents have multiple biological fathers and one mother

Anthropologists have found that polyandry—the union of one woman and more than one man—is a rarity in humans. Across thousands of studied societies, just a few dozen polyandrous cultures exist, widely scattered around the world. For the most part, the guess is that cultural factors are at work. Among rodents, however, the practice is both widespread and well understood: it cuts down on infanticide. Males who have not sired with a given female will kill her newborns to prevent the spread of his rival’s genes, and to free her from the burden of raising another’s young in favour of his own.

In a classic sexual arms-race case, the practice of polyandry won out. Males cannot distinguish their own young from a rival’s, so a female that gives birth to young from more than one male will have protected them all from any individual father’s aggression, lest he threaten his own offspring.

Natural selection, then, should have weeded out monogamy in rodents. But in the house mouse, Mus musculus, that has not happened; females can choose one or many mates. In a study published in Behavioral Ecology Yannick Auclair, of the University of Zurich, and colleagues, may have figured out why.

Mr Auclair set up and then meticulously followed the progress of a mouse colony over three years. He kept count of the litters laid, and whether they were raised in solitary nests (those that consisted of only one female and her family) or communal nests (in which females shared maternal duties, irrespective of who sired their offspring). For those pups that survived into adolescence, he took tissue samples to determine paternity by genetic analysis.

The final tally noted 146 survivors and 254 deaths among the pups. Scratch marks on the bodies suggested that almost all deaths were due to infanticide. What was more interesting, however, were the survival rates between different kinds of litters. Polyandrous litters survived well in both solitary and communal nests, but monandrous ones survived significantly more in communal nests than in solitary ones. The reason, the team concludes, is “socially mediated polyandry”. A nest full of pups from many mothers and fathers was as safe as a nest with one mother and many fathers’ pups. Females derived the protective benefits of polyandry without actually having to expend the effort to carry it out.

The authors suggest that socially mediated polyandry might apply to many more species that engage in communal care of the young, including a small percentage of mammals such as rodents. That makes it a rich seam for investigation by evolutionary biologists. The explanation for a smattering of polyandry in humans, however, remains a matter of guesswork for anthropologists.

First published on economist.com. Image by noadi. CC-BY-NC-ND.

A better writer and a better thinker

This week I started my internship at The Economist. I had been looking forward to this since the day I got the offer, and it was one my strongest motivations to submit my DPhil thesis. A number of reasons made it so. But mainly it was because I knew that the few months at The Economist are going to be an exercise in becoming a better writer and a better thinker.

Becoming a better writer may be obvious. The Economist is a very well-written newspaper, and, if I am to write for it every week, I have to better my game. But a better thinker?

Yes and here’s an analogy to explain it: When I first came to Oxford, I had just finished four years in the Institute of Chemical Technology, Mumbai. Coming to Oxford was a shock to my system in many ways. I was in a foreign country, surrounded by people from all over the world, I was moving from a taught course into research, I was going to live in a house with three girls rather than a hostel full of boys, etc. But one of things that most stood out in all those new things was that all the students at Oxford did not study chemical engineering. Actually, they studied more subjects than I could keep a count.

Exeter college, which is a very welcoming place, made sure that in the first week we had as many social engagements as were physically possible. It forced me, pleasantly so, to mix with students from many subject areas. Over the next four years, a lot of my thinking was shaped by interacting with these students.

I expect my time at The Economist to do the same for me all over again, and do it better. Even though it is only a few months, because the paper (as it is referred to in-house) writes with a single voice (if you aren’t aware, The Economist has no byline), it will force me to confront my views a lot more than I had to at Oxford. When I say ‘single voice’, I do not mean that all the writers have the same opinion, but that they arrive at one through a lot of debate. If I am to write about something, I need to be prepared to defend my stance or find something that I can defend.

Here’s what I learnt:

The start of a new week at the paper is on a Friday because that week’s paper goes to print on a Thursday afternoon. The first Friday-morning meeting is one where people float ideas for the next week to their section editors (Business, Finance, Britain, etc.), but mainly the aim that day is to think about leaders (opinion pieces) for next week. The section editors then take those ideas to the next meeting, which happens in the Editor-in-chief’s office.

Both these meetings go on for quite sometime. Especially, the second one. Leader ideas are thrown on the table and then dissected. Although most of the talking happens in between the section editors, the deputy editor and the editor-in-chief, many other people contribute. I got told on the very first day, “If you have an opinion, at The Economist you will have plenty of opportunity to air it.” It’s true. Even those writing for the science section question a finance leader and those writing for the Britain section question a leader about the Libyan election.

After a quiet weekend, Monday starts with longer versions of the Friday meetings. More discussions follow but this time they are more concrete. After all, the deadline to wrap-up the paper is only two days away i.e. Wednesday night. People use Monday afternoon and Tuesday to do the research, interviews, reporting, and on Wednesday there is a lot of back and forth between writers and editors as they polish their stories.

The working hours are very flexible, the people are very warm and the 12th floor office has a great view of the city. I got told more than once that The Economist is a weekly newspaper, which means that the stories have to have more than just ‘news value’. Not just well-written, but it also needs to be a well-analysed and entertaining story.

The week

For me, it was an unusual week. Monday through Wednesday, the science and technology team was working from home, in what was an experiment. And as it happened, I ended up being at a conference on Thursday and Friday. So although I didn’t get to interact very much with the team I am going to be working in, I got to meet a lot of other writers.

This is not to say that I did not work. Apart from attending the conference, I attended the ‘Welcome to The Economist‘ talk, ‘How to be a journalist’ talk, got trained on the necessary software, made new friends and wrote two articles, which depending on what the editors think may or may not get published (PS: I will be posting what gets published here).

Finally, I won’t be boring you with what happened at The Economist every week (for that you should read the paper). But, as always, I will write whenever I have something worthy to share. Like the ad below: