Today I Learned:
1) My Erdös* number** is 5!
* To type a "ö" on a mac, press alt+u, release both keys, then type an o. This works for any vowel, including y.
** An Erdös number is the number of degrees of separation you are from Paul Erdös by publication co-authorship. Erdös numbers are, in general, quite small, as Erdös published massive numbers of articles and was well-known for collaborating widely and extensively.
2) There is a dialect of German called Texas German, spoken by the descendants of German immigrants who moved to Texas sometime... a while ago. It sounds just like German-German to my ears, but it's a bit softer and it has experienced one or two major vowel shifts. It's also a dying tongue -- it's pretty much only spoken by older folks now.
Thanks to Anders Knight for teaching me about Texas German!
3) Let's talk about the pineal gland! I mostly know about the pineal gland because of its central role in the metaphysics of Descartes. See, Descartes was a dualist*, which means he espoused a metaphysics in which physical stuff and spiritual stuff are both real and both exist, but are causally separate -- one does not affect the other. The obvious problem with this theory is that if there are physical bodies and souls, they obviously interact SOMEHOW, since your soul can sense what happens to the body and can control it at least to some degree. Descartes' answer was that the soul interacts with the body through the pineal gland. This is a fairly silly idea. For one thing... why the pineal gland?!?!** More importantly, though, this only begs the question of how the soul interacts with the pineal gland if the pineal gland is physical... Descartes' answer to this was basically a shrug. (Lest you think poorly of Descartes, I should point out that Descartes was also the biggest single force in moving the focus of western philosophy from questions of "what do ancient sources tell us is the truth?" to questions of "what can we figure out?". Oh, and he invented algebraic geometry, which is the idea of graphing algebraic equations. Kind of a big deal.)
This came up in conversation earlier today, so I decided to go learn a little bit about the pineal gland. The pineal gland is a tiny, roughly pinecone-shaped organ deep in the brain. We don't know all *that* much about what the pineal gland does, but it does make at least several important hormones. The pineal gland's primary function seems to be maintenance of circadian rythms. What's the evidence for that? Well, the pineal gland is the primary producer of melatonin in the brain, which is the most well-known and I'm pretty sure the most well-understood, signaling molecule involved in sleep and wakefulness. Also, there are optic nerves that run directly from the eye to the pineal gland, which appear to more-or-less directly regulate melatonin levels based on light intensity.
The coolest evidence, however, comes from reptiles and some other more-basal vertebrates, who use an extension of the pineal gland as a third eye. See, the pineal gland shares a surprising amount of structure with the retina, up to the point of being sensitive to light. Many lizards, frogs, and fish have a "third eye" more or less in the middle of their foreheads (check out the wiki article on "parietal eye" for some nice pictures) that is actually an outgrowth of the pineal gland *through* the skull and just below the skin. This "parietal eye" seems to act as a direct sensor for the pineal gland to detect light, and is important for circadian rhythm and thermoregulation (which is tied to circadian rhythm) in the species that have one.
The pineal gland can be removed from humans apparently without too much effect other than screwed up sleep patterning (at least, in adults; youths whose pineal glands are damaged apparently tend to go through puberty much earlier, so the pineal gland is probably responsible for hormonal homeostasis in the young). It very rarely happens, though, because its situation deep in the brain makes it very difficult to get to safely to remove. The pineal gland also doesn't get diseased particularly often, although it *does* calcify in the majority of people. This seems to be normal, or at least common, although severity of pineal calcification does correlate with incidence of Alzheimers (I would guess because of some third cause related to brain maintenance).
Thanks to Bear Bear Bear and Andrés Muñuz for stimulating my curiosity on this subject!
* I've also heard the theory that Descartes was actually much more a physical materialist than a dualist, but that he faced potentially lethal pressure from the church to include souls in his philosophy. Under this theory, Descartes tried to establish dualism as a way to partition the spiritual as much as possible *away* from the physical so that he could talk about physical stuff without being constantly bogged down by spiritual metaphysics. If true, the whole idea of the pineal gland linking the spiritual and physical may have been a throwaway idea to push back the rather obvious question of spirit/material interaction; it may have even been chosen to highlight how silly the idea was. I'm pretty sure this theory is far outside the mainstream, but it amuses me.
** I also learned today why Descartes chose the pineal gland as the seat of consciousness. His reasoning was threefold: a) The pineal gland appears to be a single organ, where many other structures (particularly in the brain) are composed of two more-or-less identical organs in either hemisphere (this turns out to be the case for the pineal gland, too); b) The pineal gland is deep in the brain and located conveniently close to the spine, making it well-situated to quickly react to and control bodily functions; and c) The pineal gland is heavily vascularized, which would help it communicate with the body (Descartes speculated that the pineal gland sent out little corpuscular machines to influence the rest of the body). Descartes was criticized for his lack of anatomical knowledge when he wrote about that, and he has been ever since.
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