erratio

The evolution of menstruation

Tue, 08 Apr 2014 17:25:31 GMT

http://www.quora.com/Menstruation/What-is-the-evolutionary-or-biological-purpose-of-having-periods

Kind of terrifying

Choice excerpts:

"Inside the uterus we have a thick layer of endometrial tissue, which contains only tiny blood vessels. The endometrium seals off our main blood supply from the newly implanted embryo. The growing placenta literally burrows through this layer, rips into arterial walls and re-wires them to channel blood straight to the hungry embryo. It delves deep into the surrounding tissues, razes them and pumps the arteries full of hormones so they expand into the space created. It paralyzes these arteries so the mother cannot even constrict them"

"This might seem rather disrespectful. In fact, it's sibling rivalry at its evolutionary best. You see, mother and fetus have quite distinct evolutionary interests. The mother 'wants' to dedicate approximately equal resources to all her surviving children, including possible future children, and none to those who will die. The fetus 'wants' to survive, and take as much as it can get. (The quotes are to indicate that this isn't about what they consciously want, but about what evolution tends to optimize.)

There's also a third player here – the father, whose interests align still less with the mother's because her other offspring may not be his. Through a process called genomic imprinting, certain fetal genes inherited from the father can activate in the placenta. These genes ruthlessly promote the welfare of the offspring at the mother's expense."

"Far from offering a nurturing embrace, the endometrium is a lethal testing-ground which only the toughest embryos survive. The longer the female can delay that placenta reaching her bloodstream, the longer she has to decide if she wants to dispose of this embryo without significant cost. The embryo, in contrast, wants to implant its placenta as quickly as possible, both to obtain access to its mother's rich blood, and to increase her stake in its survival. For this reason, the endometrium got thicker and tougher – and the fetal placenta got correspondingly more aggressive.

But this development posed a further problem: what to do when the embryo died or was stuck half-alive in the uterus? The blood supply to the endometrial surface must be restricted, or the embryo would simply attach the placenta there. But restricting the blood supply makes the tissue weakly responsive to hormonal signals from the mother – and potentially more responsive to signals from nearby embryos, who naturally would like to persuade the endometrium to be more friendly. In addition, this makes it vulnerable to infection, especially when it already contains dead and dying tissues."

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More on language and memory

Thu, 14 Jul 2011 04:17:12 GMT

So it turns out I misremembered the study I saw about children not being able to lay down memories without language. The study I meant to refer to actually shows that children could only describe events using the vocabulary they had at the time the memory was encoded. Which in younger children meant that they couldn't describe it verbally at all. However, they were able to remember it, as evidenced by their ability to re-enact it and recognise photos of the activity involved.

And studies of young children involving conditioning show that even very young children are perfectly capable of remembering things (see this paper which includes a description of tying a baby's foot to a mobile with string so that it could entertain itself, and then checking how long some string or the mobile would elicit the learnt kicking motions), so it's not that children are incapable of remembering events per se. (although that paper does note that their memory of the mobile/string thing only lasted for a few weeks at the outer limit).

There's a bunch of other research out there, but most of it isn't solid and/or is hidden behind paywalls, so it's difficult to really check. But it looks like the 'context-specific' explanation is the leading one so far. I'd be really interested in trying to find other people who've undergone relatively severe paradigm shifts in the way they think, and see whether their memory from before the paradigm shift is worse than you would normally expect for older memories. Or is the preverbal -> verbal shift the only one big enough to potentially make all the previous states of mind completely inaccessible?

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Misconduct in science

Mon, 11 Jul 2011 12:59:44 GMT

Who'da thunk it that scientists are just as prone to cheating as people in other professions? A Nature article(non-paywalled version) found that around a third of around 3000 respondents admitted to having engaging in some kind of scientific misconduct, ranging from falsified data to the comparatively benign sin of not keeping proper records related to research projects.

Looking at the percentages of people confessing to various behaviours puts me strongly in mind of one of Dan Ariely's studies, documented in Predictably Irrational, where he gave people tests with monetary rewards for correct answers, and then progressively made it easier for each subsequent group to cheat. His overwhelming conclusions were a) that people will cheat if you let them, but only up to a certain point, and b) that removing money from the equation by, for example, giving the participants tokens that were exchanged for money just a minute or two later, greatly increased the incidence of cheating because money is Serious Business.
We can see the same kind of cheating going on here, with relatively large numbers of respondents admitting to some kind of misconduct, but most of it being of the minor easy to rationalise variety and further away from the parts of their work that really pay their salary (funding and publishing). For example, 7.6% of all respondents admitted to circumventing minor aspects of human-subject requirements but only 0.3% circumvented major aspects. Similarly, almost no one failed to disclose involvement in firms whose products were based on their research (0.3%) but around 15% allowed funding sources to pressure them into changing their design, methodology, or results, despite the same type of objectivity being called for.

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