Reproductive quirks (part 2): Why did menstruation evolve?

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A glass of red wine. Photo taken in Montreal C...

Women lose about 90 millilitres of blood each month. The question is, why? (Photo credit: Wikipedia)

As I’ve noted previously, humans are strange beasts and our reproductive biology illustrates this well. Menstruation and menopause are both rare in the animal kingdom. Of all mammals, only us, our primate relatives and elephant shrews menstruate. Menopause is even harder to come by — killer whales are our only sisters in hot-flushes, apparently.

This begs the question: why? How did each of these reproductive quirks evolve in humans?

I’ve written two pieces for The Conversation about the evolutionary theories that try to explain where menopause and menstruation come from. The first, about menopause, can be found here. The second, on why women menstruate, has also now been published. 

Same genes, different body: the making of a queen

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English: Biston betularia caterpillars on birc...

An example of polyphenism: Biston betularia caterpillars on birch (left) and willow (right). (Photo credit: Wikipedia)

How tall are you? Almost everyone I know (myself being an exception) is taller than their same-sex parent, who is, in turn, taller than their same-sex parent. Over recent generations, average height has increased in many parts of the world. This is far too quick to put it down to an evolutionary change based on shifting genetics. Most of us are taller than our parents and grandparents because of our environment — better nutrition, fewer diseases, and less hard labour in our developing years.

But if you really want to see what environmental cues can do to body shape and function, consider the case of social insects. The environment in which a larva is nurtured determines whether it goes on to be a queen or a worker. The caste system of insects is an example of a phenomenon called polyphenism, where the same set of genes (genotype) can result in vastly different body forms (phenotypes). Unlike height in humans, which varies along a continuum, polyphenism in insects creates discrete types. There’s no half-way point between worker and queen; you’re either one or the other. In the one case, you are bound for reproductive glory, in the other, you remain sterile.  Continue reading →

Reproductive quirks (part 1): Why did menopause evolve?

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my grandmother

Women go through menopause when they still have a third of their life ahead of them (Photo credit: paul goyette)

Humans are oddballs in the animal kingdom for many reasons, but one of the quirkiest things is how we reproduce. Or, more to the point, how our bodies behave when we aren’t reproducing. Menstruation and menopause are both very rare. Of all mammals, only us, our primate relatives and elephant shrews menstruate. Menopause is even harder to come by — killer whales are our only sisters in hot-flushes, apparently.

I’ve written two pieces for The Conversation about the evolutionary theories that try to explain where menopause and menstruation come from. The first, about menopause, is out today. Check it out!

Michael Douglas, oral sex and cancer — the facts about HPV

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English: Michael Douglas At just 8000 genetic letters in length, the human papillomavirus (HPV) may be small — compare this with the 3 billion–odd letters of the human genome — but it can pack a mean punch. Some members of the HPV family of viruses are oncoviruses, meaning that they can lead to cancer. But if you’ve heard of HPV’s cancer-causing properties, you’ve probably heard it in the context of cervical cancer. Yesterday, Michael Douglas announced that his throat cancer was the result of infection with HPV. This afternoon, I was asked to write a piece for the Conversation about Douglas’s ‘cunnilingus caused my cancer’ confession — read it here.

Caring and sharing: captive wallaby microbes share genes with keepers’ microbes

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Petrogale penicillata ; Featherdale Wildlife P...

Brush-tail rock wallabies — an endangered species (Photo credit: Wikipedia)

Each of us is home to a complex ecosystem of microbes that took up residence on or in us as soon as we emerged from our mother’s womb. In fact, our passage to the outside world — whether via vaginal birth or C-section — makes a significant contribution to the  bacteria, fungi and viruses that become our constant life companions. Collectively, they are known as our microbiota, and by the age of three, the ecosystems that we harbour on every patch of skin and turn of the intestine are very similar to those of our parents.

While it may not be surprising that parents share microbes with their kids, researchers at Macquarie University in Sydney have found that animal handlers may be sharing their microbes with their furry captive charges. In doing so, keepers working in captive breeding programs could be unwittingly releasing more back into the wild than they had planned. Top on the list of unintended releases are antibiotic resistance genes.  Continue reading →

Prey to temptation: Our struggle with irrational health choices

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Smoking

Making healthy choices isn’t always easy (Photo credit: Wikipedia)

We all like to think of ourselves as rational individuals — making decisions according to the best available information for a beneficial outcome. But over the past few decades, the burgeoning field of behavioural economics has made it abundantly clear that humans are not always rational beings. In many of the financial decisions we make, we fall victim to the mental short-cuts and ‘rules of thumb’ that govern our behaviour. We end up making decisions that seem to defy logic, and work against our own long-term goals and desires.

Work by Daniel Kahneman and his late colleague Amos Tversky and others that integrated behavioural psychology with economics earned Kahneman the Nobel Prize in Economic Sciences in 2002. Researchers are now looking at how the principles of behavioural economics can be applied to fields beyond finance, to understand how we make decisions in other areas of life. And what better field than health, where we often struggle to make the right choices — often despite a plethora of available information.

In the latest episode of Up Close, I was joined by Professor Ichiro Kawachi, to discuss how behavioural economics can be applied to public health and health behaviour change. Ichiro Kawachi is Professor of Social Epidemiology, and Chair of the Department of Social and Behavioral Sciences at the Harvard School of Public Health.

Mosquitoes infected with malaria find humans more aromatic

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Anopheles gambiae mosquito Deutsch: Anopheles ...

Anopheles gambiae mosquito (Photo credit: Wikipedia)

The fragrant waft of a black lentil dhal, the acrid perfume of newly laid bitumen, the delectable aroma of freshly ground coffee beans. Smells make the world a richer, safer and more memorable terrain than it would be without our olfaction in tact.

And we’re certainly not the only ones. Indeed, when it comes to olfactory fortitude, our abilities pale in comparison to some of nature’s aroma-detecting titans. Whereas human olfactory senses — and the number of olfactory receptor proteins in our noses — have been whittled away in favour of a large visual cortex, the truffle-foraging pig and the smell-a-rabbit-two-days-after-it’s-passed-by bloodhound have evolved extraordinarily keen senses of smell.

Continue reading →