Is human longevity due to grandmothers or older fathers?

Why do humans tend to live such a long time? Our closest relatives, the chimpanzees, can last into their mid forties in the wild. Yet somewhere in the last six million years, human lifespans have lengthened dramatically, so that living into our seventies is no big surprise.

The last few weeks have seen some exciting new developments in this area. First, a recent paper featured in The Conversation showed that at all ages, humans are less likely to die than chimps.

Excitingly, however, modern health care, diets and the steady decline in violent deaths have slashed mortality rates of young adults. People in societies like Japan are now almost 200 times less likely to die in at a given age than people of the same age in hunter-gatherer societies.

The dramatic declines in modern mortality rates are almost entirely due to technological developments, but the lengthening of the maximum potential human lifespan since we diverged from the other great apes poses an intriguing evolutionary problem.

Our bodies only function as well as they do because we have a quiver-full of cellular repair and maintenance mechanisms. For example, we have systems that correct mistakes in DNA replication, and others that detect and kill off pre-cancerous clusters of cells.

But natural selection optimises those mechanisms to operate during our expected lifespan. Modern people who live beyond seventy are much more likely to suffer from cancers, dementia and other diseases of old age. Few of our ancestors – even the most recent ones – lived that long, and these late-onset diseases didn’t interfere with their successful reproduction. By the time they got the diseases, our ancestors had already passed their genes on – and that’s why we carry those same genes.

Six million years ago, the diseases of old age probably kicked in before our great-ape ancestors hit forty. The evolution of a longer lifespan involved a steady postponement of ageing. But only if older individuals contribute to the success of their own genes can this actually happen. Continue reading Is human longevity due to grandmothers or older fathers?

Romney, the single mom and the AK-47

Watching the US Presidential election from afar feels a bit like watching reality television. It seems interminable and very little of what the characters say seems to make sense.

On that front, at least, Tuesday night’s second debate between Barack Obama and Mitt Romney didn’t disappoint. While Mitt’s incomprehensible and disingenuousbinders full of women” gaffe set records as an instantaneous meme, I was more staggered by his bizarre pirouette on the question of assault weapons.

Each candidate was asked what they would do to keep assault rifles off the streets. Romney, after first reassuring everyone, including the National Rifle Association who have endorsed him, that he would not be introducing any new gun-control legislation, turned to those reassuring ideas of the do-nothing politician: “Education”, and “changing the culture”.

If you can afford the two minutes it takes, then watch his whole answer:

So profoundly does Romney believe in the changing of culture, that he pivoted directly to a beloved conservative talking point: single mothers.

Gosh, to tell our kids that before they have babies, they ought to think about getting married to someone, that’s a great idea. Because if there’s a two-parent family, the prospect of living in poverty goes down dramatically. The opportunities that the child will, will be able to achieve increase dramatically. We can make changes to the way our culture works, to help bring people away from violence and give them opportunity.

The comment, even with Romney’s mumbled qualifier (“lotta great single moms, single dads”), single parents – at least those who weren’t working an extra shift or putting their kids to bedtook offense.

Any doubts about whether Romney’s social conservatism is genuine should have been erased right there. The urge to blame single and unmarried parents for the most spurious of problems doesn’t get any more reflexive than that.

I have a couple of problems with Romney’s comment, and more generally with the Republican inability to resist treating single mothers as though they carried the plague.

First, they commit the high fallacy of extrapolating from correlation to causation. Are single parents more likely to be poor as a consequence of their relationship status, or are they more likely to be single parents as a consequence of their poverty? I’m happy to admit the links are probably complex and the flow may be bi-directional. But even if you could show that becoming a single parent caused the poverty, you would need to convince me that somehow, gosh, telling our kids that they should marry, would reduce poverty and violence.

More importantly, and here is where evolutionary psychology and evolutionary economics come into their own. These sciences (science, and especially evolution being another Republican weak point) suggest that the very core of Republican doctrine – their positively misanthropic policies on welfare, health care, family planning and taxation – reinforce the links between poverty, single parenthood and violence.

As economist Bestsey Stevenson tweeted:

Do you know how to support 2 parent families? Give both moms & dads a safety net: health insurance, paid sick leave, good middle class jobs

Sounds a lot like Obama’s platform to me.

At a deeper level, the surest way to reduce teen pregnancy and the number of young, poor, unmarried mothers (and I think these are the mums Romney blames for gun violence – rather than unwed uber-mum Angelina Jolie) is to reduce income inequality.

I have written about this before, when Mike Huckabee (remember him) got all hot and bothered about Natalie Portman giving birth before she had swanned down the aisle.

First things first: Why do women become single moms? Mostly, it isn’t a choice. Or at least the kind of choice wealthy politicians make, like “Do I cut support for Planned Parenthood, or raise taxes on the richest 1% of citizens”. For many women, the choice is between raising a child alone or not having a family at all; or between leaving an indolent or violent spouse or staying in a situation that is worse than single motherhood.

The number of single parents is, among other things, a symptom of:
– the inequalities in wealth between the rich and the poor, – whether women (particularly poor and marginalised single women) have access to contraception and safe abortion.

It seems to me that the policies Republicans hold most dear, including a bronze-age approach to family planning, and welfare and tax policies that favour the wealthy at the expense of the middle class and the poor, might be the root causes of the burgeoning infestation of single parenthood that threatens to overrun the American way of life.

Inequality isn’t just a correlate of rising numbers of poor, single mothers. It is a cause. And, among many other things that inequality causes, it also causes violence – specifically the kind that involves angry young men killing other angry young men.

And when the violence claims the lives of young men, and sends others to prison, that also pushes up the number of single mothers by creating a shortage of men. Young women and girls have to compete among themselves for the few marriageable men available. And that means having sex earlier and more often, and under less ideal circumstances than they otherwise might have. And that occasionally leads to pregnancy and single motherhood.

These are exactly the circumstances in which women need affordable contraception, discreet family planning services and safe abortion.

So, how best could the winner of this election reduce both the number of gun-related deaths and the number of single mothers?

For one thing, he could stand up to the plutocrats and work to narrow the deepening income chasm between rich and poor. For another, he could stand up to the evangelicals and ensure that women have affordable contraception and that on those rare occasions when a poor and desperate woman needs to terminate an unwanted pregnancy, she can do so safely and without harassment.

I’m not sure the even Mitt Romney could land that pirouette.

Rob Brooks does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

The Conversation

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The short-lived feminism of Tony Abbott



I couldn’t help but be captivated by Prime Minister Gillard’s speech against the motion to remove Peter Slipper as Speaker of the Federal Parliament yesterday. Like the majority of people I tend to follow on social media, I was thrilled to see the Prime Minister speaking from the heart about sexism.

Having watched Christopher Pyne’s sexist treatment of Kate Ellis on Q&A on Monday (see Ben Pobjie’s excellent analysis), I couldn’t decide whether to watch Abbott or Pyne as the Prime Minister handed them their medicine.

This wasn’t quite Cicero denouncing Catiline in the senate. Not least because of the pathetic sordidness of the Peter Slipper affair. And commentators who followed the full day’s incendiary proceedings have a less glowing assessment of the speech’s impact than those of us who saw only the speech itself.

But what excited me, and no doubt animated the video’s viral spread, is the way in which the Prime Minister stood up to Tony Abbott’s aggressive, bullying political style.

Much has been made of Abbott’s so-called “problem with women”. I have no knowledge of how he personally relates to women. But with the way in which he has conducted himself as opposition leader, he has earned the public perception that he has a problem with women, especially women in authority.

He wields his robust aggression so effectively in trying to dislodge and disrupt the government. But now that it is harming his standing with voters, he’s suddenly attempted to remake himself as a feminist. Last week Abbott’s wife, Margie, stepped up to rebut the idea he’s on “some kind of anti-women crusade”. She even went so far as to call him a feminist.

Yesterday, when he got the chance he has been begging for, to move that Peter Slipper be removed as speaker, he made his case on the basis of Slipper’s gross sexism. Suddenly, when the polls start telling him that his perceived sexism is costing him votes, Abbott reveals that he’s a feminist. The last time I was so surprised at a coming-out was when the Insane Clown Posse announced they were actually evangelical Christians.

Abbott’s is the kind of clumsy “re-branding” that only a PR zombie who has never actually met a real voter could have dreamed up. Nobody builds feminist cred overnight. Having a wife and three daughters doesn’t confer it. Especially when Abbott admits to having told his daughters that their virginity is “the most precious gift” they could give someone.

Perhaps, as some regular readers of this column like to point out, I read too much sex, gender and reproduction into modern affairs. Perhaps I should stick to thinking about sexual conflict in other animals.

But then I look at politicians like Tony Abbott and Cory Bernardi here in Australia, and Todd Akin and Paul Ryan in the USA, and I cannot help but see the narrow reproductive self-interest that permeates so much of their politics.

If you talk and behave like a man who has never given a moment’s thought to what it is like to live as a woman, then the best you can hope for is to represent other men who have given just as little thought to what life is like for their daughters and wives (should they be so lucky).

And if you speak and think like someone who has never considered what it is like to be gay, then don’t act surprised when gay people actively oppose your re-election.

And if, like Alan Jones, you make your considerable living giving a life-like rendition of a bully who exploits their listener’s self-interest, then don’t whinge about cyber-bullying when the public push back at you.

I grow ever more convinced – although I don’t have the evidence for this yet – that women and men each inherit a kind of gendered myopia that makes it difficult to empathise completely with members of the opposite sex. Which makes it genuinely difficult for us to truly understand one another. Abbott, Jones and the like have built their careers catering to men who’ve spent their lives not thinking deeply about the lives their daughters and wives lead, or would like to lead.

If Tony Abbott wants to undo his damaged reputation with women, he needs to start in the right place. Simply calling yourself a feminist will only lead to more trouble.

Which is one of the reasons I so enjoyed the Prime Minister’s speech. She called Abbott on his rank hypocrisy in trying to paint himself as a feminist when it suddenly became expedient to do so. And, as Anthony Sharwood put it at The Punch, Tony Abbott “got owned”.

Rob Brooks does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.

The Conversation

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Your cat has toxoplasmosis and you’re worried? Join the club.

I should admit straight up that I’m no fan of cats. Like any zoologist I treasure the rare glimpses I have had of lions, leopards, serval and even ocelot.

But I have never understood the devotion of so many seemingly-rational people to a domestic animal that oozes disdain, dispenses allergy and destroys wildlife with such abandon.

Which is one of the many reasons I relish each new scientific finding regarding the protozoan parasite Toxoplasma gondii and its intriguing effects on humans.

Cats are essential to the life-cycle of this insidious parasite. As the evidence mounts of the havoc Toxoplasma wreaks when it infects humans, I naively imagine people will grow less enthusiastic about keeping cats.

But despite recent studies linking Toxoplasma to schizophrenia and brain cancer, cat ownership is not a huge risk factor. So cat-lovers don’t look likely to get rid of their pets.

As with its close relative, the malaria-causing parasite Plasmodium, Toxoplasma undergoes the sexual part of its life cycle in one host and a period of asexual reproduction in another.Meet Toxoplasma gondii
The all-important sexual stage happens inside the gut of a cat, whereas the asexual stage can happen in any mammal or bird.

Most often this intermediate host is a rodent that has eaten food contaminated by cat feces. But humans commonly become infected, usually due to poor hygiene and food preparation.

Infection can be catastrophic for patients with compromised immune function and for foetuses whose mothers suffer a new Toxoplasma infection during pregnancy. But most infections involve a brief, mild flu-like illness. Around one in three people worldwide, and as many as 80% of people in some countries have antibodies to T. gondii, indicating they have previously been infected.

After infection, the parasite doesn’t go away. It forms cysts inside muscle cells and neurons, where it avoids the host’s immune system. These cysts don’t seem to cause any immediate trouble and, until recently, nobody paid them much attention.

Rat, meet cat

The interesting thing about so many parasites is the way they manipulate a host’s behaviour to their own advantage. People with colds, for example, emit impressive volumes of snot, often sharing it in aerosol form. That virus-sodden liquid isn’t merely an unhappy side-effect of the infection. It is an adaptation – on the part of the virus rather than the human. Viruses that cause runny noses and sneezing make the leap from host to host, whereas more considerate viruses might never propagate themselves. As a result, natural selection leaves us with the inconvenient kind of virus.

Continue reading Your cat has toxoplasmosis and you’re worried? Join the club.