The language of evolution on trial

Humans are purpose seeking beings. Such a fact is nowhere more apparent than in our language. Some scientists argue that this tendency is a cause of confusion in their subject, especially when it comes to descriptions of evolution. The teleological turn of phrase is so tempting because of how much easier it is to read and understand than a dry purposeless, but more accurate, expression.  ‘Wings evolved for flight’ isn’t quite right but we understand the message. I remember my chemistry teacher’s classes were replete with teleology, ions wanted to gain or lose electrons so they could balance their charge. But of course, none of us believed for a second that the atoms intended to do this. All there was to it were the blind forces of the atomic world. So it goes for evolution as our current understanding of the process is teleology free.

Richard Dawkins, who was put on this Earth to popularize evolution, is always quick to correct himself when his tongue slips to purpose. But I would argue that our linguistic short-cuts are not the primary cause of the public misunderstanding of evolution. It was Eugenie Scott who said for many people the problem behind evolution is not one of confusion, rather it’s a full understanding and disgust at the implications of it. Some of us don’t like the idea of being a ‘mere’ animal. Of course language matters but it would be a shame for us to avoid using language which can convey an idea so succinctly when it’s not to blame. Perhaps I’m being overly naïve here and we’re adding to the confusion with our lack of precision. So I’m open to debate on this one. What do you think?

Author

Adam Kane: kanead[at]tcd.ie

Photo credit

wikimedia commons

Cod, correlation and causation

so help you Cod

 at the Guardian reports on a battle between science and politics which is worth highlighting. The Atlantic cod fisheries in the Atlantic collapsed during the 90s due to overfishing. They have yet to recover. The Atlantic cod is an apex predator and its decline effected a trophic cascade, which modified the original food web, perhaps irrevocably.

The Canadian government is holding the grey seal responsible for this. They argue that the seals, which are growing in number, are preventing the recovery of the stocks and are planning to kill 70,000 of them next year.

This has vexed a group of marine biologists at Dalhousie University so much that they wrote an open letter arguing that cod are rarely preyed upon by the seals. Instead, the cod’s main predators are other, larger fishes. And in actual fact, the seal preferentially feeds on these fishes. So any reduction in seal numbers will produce the opposite result to the one intended, seals will be killed, the predatory fish population will increase, and the cod population will decline even further.

Correlation does not imply causation. But perhaps, the view of the Canadian government is that of Winston Churchill who once remarked, scientists should be on tap, not on top.  It will be interesting to see how this one plays out.

Author

Adam Kane: kanead[at]tcd.ie

Photo credit

wikimedia commons

A dose of Darwin

One of the more irksome aspects of life is getting sick, I always think we should be beyond this. When it comes to medicine I suppose we can ourselves lucky to be alive at a time when doctors and butchers are no longer interchangeable. But even in the 21st century we’re still engaged in arms races with bacteria and chemical warfare with cancer (military metaphors are never in short supply) . Bacteria evolve resistant strains to our best antibiotics and tumours do likewise against our attempted cures. Less grave but still illustrative is the perennial persistence of the common cold. Illness comes in many forms, wellness only one. The main problems we face in trying to create cures is that all pathogens are evolving and to realise that we too have evolved. We often end up using static measures against dynamic problems.

That said, I think this century will see some considerable advances in medicine owing to the increasing use of evolutionary insights to combat disease. This is the science of evolutionary medicine.

Some of the symptoms we most associate with being sick like fever, pain, nausea and vomiting aren’t from the disease per se, but the body’s defences in action. Randolph Nesse, who wrote the book on evolutionary medicine, says that medical doctors would do well to recognise our evolutionary origins when treating their patients.

Our biology is playing catch up to our cultural advances and this lag period can explain many modern afflictions. Nobody reading this suffers from prolonged periods of hunger but we still stuff our faces when we get the chance. Of course, before modern civilization our next meal wasn’t always a sure thing, so gorging when the going is good was the way to go. The upshot of this is a significant proportion of the developed world is obese.

Some of the ideas of evolutionary medicine seem to run counter to our regular approach and our intuition. For instance, when treating a patient with chemotherapy, we use the most potent chemicals and this seems perfectly reasonable. We want to hit the tumour hard and fast. In fact, all we do then is put a strong selective pressure on the tumour cells to evolve resistance, ultimately shortening the patients’ lives. Instead, we should only give the minimum dose necessary to keep the cancer under control.

Fleming’s discovery of penicillin is one of those instances of serendipity that turned out to be a great boon for medicine. But I’d prefer not to rely on serendipity if you don’t mind! It would be far preferable to know why how and why diseases arise. Bernard Crespi is doing this with his research on schizophrenia and autism. Crespi argues that these disorders are diametrically opposed, autism is the result of an underdeveloped social brain whereas schizophrenia comes from a hyper-developed one. They are caused by the abnormal expression of imprinted genes, i.e. ones expressed according to the parent they came from. If true, then we can use opposing treatments to treat these twinned disorders.

Unfortunately, as Richard Dawkins puts it, we evolved to be fecund not necessarily to be healthy. Any competition between the two and the latter won out. But now at least we know that’s the case and we can do something about it.

Author

Adam Kane: kanead[at]tcd.ie

Photo credit

Dr. Barbara Natterson-Horowitz

Zombies and the problem of consciousness

Seeing as it’s Halloween, I’m going to play devil’s advocate with the help of some zombies and explore the Gordian knot of consciousness. I think most scientists would hold a physicalist view when it comes to their view of how the world ‘really’ is. That is to say, objectively speaking, all there is to the universe are the various interacting fields and particles of physics. The problem with such a view is that our conscious selves prove very difficult to incorporate into this picture. We are subjective beings. Finding out how consciousness came about is known as the hard problem of consciousness.

David Chalmers, a philosopher of mind, formed a clever thought experiment to illustrate the difficulty. Okay, so imagine a world where everyone has the outside appearance of being conscious, for instance they laugh when you tell a joke,  shirk away from pain, gaze at sunsets etc., the only difference is that they have no internal subjectivity, they’re automata or zombies. I don’t see any problem with conceiving of such a place, so it looks like a possibility. But if these automata are indistinguishable from us on the outside in terms of their behaviours and actions then evolution won’t be able to distinguish between them and us, so why consciousness? It looks like an unnecessary extravagance. It also suggests that there is something more to the world than the physical, because our world isn’t like that, we, or at least I, know I’m conscious.

It seems to me that our theories as to how and why consciousness evolved have fallen short in their efforts. A lot of work is dedicated to finding the neural correlates of consciousness, but that doesn’t get us anywhere! Neurons are made up of the same material as the rest of the cells in our body, but heart cells don’t generate conscious beings so why treat neurons differently. So we’re really left with two questions. How do physical things generate subjective thought? And once we get there, why is it advantageous to be conscious? It’s called the hard problem for a reason.

Author

kanead[at]tcd.ie

Photo credit

wikimedia commons


“To expect the unexpected shows a thoroughly modern intellect”

I spoke before of how to use mathematics to convey an idea in biology. Here, I’ll take a different tack and discuss a paper in which the author makes his argument with naked English. The author in question is Nicholas Humphrey who in his famous paper ‘The social function of the intellect’ draws a wonderful metaphor of Mother Nature as an economist,

“It is not her habit to tolerate needless extravagance in the animals on her production lines: superfluous capacity is trimmed back, new capacity added only as and when it is needed”.

His metaphor serves as an introduction to the puzzle of the seemingly unnecessarily inflated intellects of some animals, notably humans.

Humphrey questions if such a highly developed intellect is really necessary for invention. The ability to produce tools is generally not a result of deductive reasoning or creative thought but rather follows from aping other individuals or pure trial and error learning. The intellect must have some other function in his estimation and in the end, he proposes that it is as a social glue. The complex interactions that arise out of the social milieu require some serious intellectual horsepower,

“[S]ocial primates are required by the very nature of the system they create and maintain to be calculating beings; they must be able to calculate the consequences of their own behaviour, to calculate the likely behaviour of others, to calculate the balance of advantage and loss – and all this in a context where the evidence on which their calculations are based is ephemeral, ambiguous and liable to change, not least as a consequence of their own actions.”
 

Calculating the consequences of your own behaviour is one thing but understanding that others around you have motivations of their own is a huge leap in understanding. All of this is done without ever having direct access to the subjective thoughts, motives, and desires of another person. Understanding the reasons for understanding is even more impressive and Humphrey’s paper has rightly influenced the theories of scientists since its publication. Most recently a study in the school that mechanistically linked sociality and selection for intelligence.

Author

Adam Kane: kanead[at]tcd.ie

Photo credit

Wikimedia commons

Hot heads lead to hot flashes: the evolution of menopause

A new study has been published online in Ecology Letters by Mirkka Lahdenperä and colleagues, which suggests that competition between grandmothers and their daughters-in-law may explain the evolution of menopause. The study used a 200-year dataset of births, deaths and residency patterns in pre-industrial Finland to show that competition between unrelated females of different generations was a key component of selection for menopause.

Humans are among only four species known to lose their ability to reproduce long before they die; the others being killer whales, pilot whales and one aphid species. This phenomenon of menopause poses somewhat of an evolutionary conundrum: how could the loss of the ability to reproduce increase an individual’s fitness?

One possible answer was suggested by Cant & Johnstone, based on differences in how related a mother and daughter-in-law are to each other’s offspring. Historically, females of reproductive age usually leave their family to co-habit with their spouse’s family in most human societies, while males stay near their parents. This means that elder females are typically unrelated to next generation of reproductive females in their locale. Thus, it is expected that young females should invest in competition with their mother-in-law, while the elder mothers-in-law may be selected to cease investing in reproduction and instead invest in helping to raise their related grandchildren.

The new study by Lahdenperä et al. showed that when a mother and daughter-in-law reproduce at the same time offspring survivorship is reduced by up to 66%, while simultaneous reproduction by a mother and daughter had no effect. These patterns suggest that a daughter and mother-in-law compete strongly for resources for their children, as predicted by Cant & Johnstone.

The authors also used their data to parameterise a kin selection model to show that selection should favour menopause around the age of 50 in order to reduce this conflict. This study provides an excellent example of how theory and data can be combined to tackle evolutionary problems, and provides insight into one of the great peculiarities of the human species.

References

1. Lahdenperä M, Gillespie DOS, Lummaa V, Russell AF (2012) Severe intergenerational reproductive conflict and the evolution of menopause. Ecology Letters. (http://onlinelibrary.wiley.com/doi/10.1111/j.1461-0248.2012.01851.x/abstract)

2. Uematsu K, Kutsukake M, Fukatsu T, Shimada M, Shibao H (2010) Altruistic colony defense by menopausal female insects. Current Biology 20: 1182-1186. (http://www.sciencedirect.com/science/article/pii/S0960982210006391)

3. Cant MA, Johnstone RA (2008) Reproductive conflict and the separation of reproductive generations in humans. Proceedings of the National Academy of Sciences 105: 5332-5336. (http://www.pnas.org/content/105/14/5332)

4. http://en.wikipedia.org/wiki/Kin_selection

Author

Luke McNally: mcnalll[at]tcd.ie

Photo credit

Wikimedia Commons