CapitalistImperialistPig

Stress in early childhood produces a flood of glucocorticoids that permanently damages brain development, resulting in impaired cognition and emotional regulation. Thus, childhood adversity can atrophy and blunt the functioning of the hippocampus and frontal cortex. But it’s the opposite in the amygdala— lots of adversity and the amygdala becomes larger and hyperreactive. One consequence is increased risk of anxiety disorders; when coupled with the poor frontocortical development, it explains problems with emotion and behavior regulation, especially impulse control.  Sapolsky, Robert M.. Behave: The Biology of Humans at Our Best and Worst (p. 251). Penguin Publishing Group. Kindle Edition.  The worst stressor seems to be an abusive mother, or being separated from the mother at an early age, but all sorts of other adversity (poverty, lead poisoning, etc.) seem to have similar results.

Humans have relatively big brains - even modern humans with our brains 25% smaller than that of a Neandertal.  Our eighty-six billion or so neurons sounds impressive compared to a fruit fly's 250,000, but maybe not so much so compared to the honeybee's roughly 1 million.  After all, we weigh about a million times as much as a honeybee, but our neuron count is less than 100,000 times larger.  So who's the real brainiac?  On an absolute size scale, our brains and neuron count are dwarfed by the brains of elephants and whales.  Numerous birds best us on the brain size to body size scale, as do many primates. So why are we driving all them and perhaps ourselves to extinction, instead of vice-versa?  The answer probably lies in our exceptional capabilities to cooperate and in our technology.  Of course ants and bees are at least equally good at cooperation, but they are too small to control fire.  Fire is not available to whales either.

In addition to remembering stuff, our brains are busy forgetting about other stuff.  It turns out that forgetting is not a purely accidental process, its an active process, pruning the memory collection.  Memories deemed useless, obsolete or significantly redundant are actively suppressed.  Interestingly enough, these processes seem to be essentially the same in the 250,000 neuron fruit-fly brain and our own with roughly 86 billion neurons. This process is discussed in Spolsky's Behave , a book I've been reading and writing about lately, but some new research is featured in Quanta here. One form of active forgetting that scientists formally  identified in 2017 is called intrinsic forgetting. It involves a certain subset of cells in the brain — which  Ronald Davis  and  Yi Zhong , who wrote the paper that introduced the idea, casually call “forgetting cells” — that degrade the engrams in memory cells. There are others.  It seems that at least ...

Steve Hsu has been considering correlations between a polygenic index and college completion rate.  It appears that the genes are rather predictive of college completion.  Steve constructs this scenario: You are an IVF physician advising parents who have exactly 2 viable embryos, ready for implantation.  The parents want to implant only one embryo.  All genetic and morphological information about the embryos suggest that they are both viable, healthy, and free of elevated disease risk. However, embryo A has polygenic score (as in figure above) in the lowest quintile (elevated risk of struggling in school) while embryo B has polygenic score in the highest quintile (less than average risk of struggling in school). We could sharpen the question by assuming, e.g., that embryo A has score in the bottom 1% while embryo B is in the top 1%. You have no other statistical or medical information to differentiate between the two embryos. What do you tell the parents? Do you...

Humans have achieved 85% of adult brain volume by age two, but the brain is not fully "wired" until the mid-twenties, long after sexual and other physical maturity.  This has important consequences. Think about this— adolescence and early adulthood are the times when someone is most likely to kill, be killed, leave home forever, invent an art form, help overthrow a dictator, ethnically cleanse a village, devote themselves to the needy, become addicted, marry outside their group, transform physics, have hideous fashion taste, break their neck recreationally, commit their life to God, mug an old lady, or be convinced that all of history has converged to make this moment the most consequential, the most fraught with peril and promise, the most demanding that they get involved and make a difference. In other words, it’s the time of life of maximal risk taking, novelty seeking, and affiliation with peers. All because of that immature frontal cortex. Sapolsky, Robert M.. Behav...

While temperatures around the world are setting record highs, wildfires, and killing vulnerable people , the Arctic is having a relatively slow melt year.  No doubt this will be seized on by the usual suspects to "prove" that the long promised "recovery" is here, all the larger melts (at this point) are from the last eleven years, so it surely looks a lot more like a fluctuation.

The second most famous idea in extraterrestrial biology is the Drake Equation.   The idea of the Drake Equation is to express the probability of finding ETs as a product of presumably independent factors (fraction of stars with planet, fraction of planets suitable for life, probability of life arising on a suitable planet, etc.)  When the equation was first written down, none of these factors were known.  We now know that planets are common - there are many billions in our galaxy and perhaps trillions.  We can't be sure yet, but it looks like something like a billion ought to be broadly suitable for life. The fact that life arose nearly as soon as it possibly could have on Earth suggests but doesn't prove that life is likely to arise on suitable planets.  Experimental biophysics and biochemistry seem to be converging on an explanation of how life arose one Earth, but large - enormous - uncertainties remain.  Much of this uncertainty could be removed if we...