SMF

I agree, nicely stated Doc Rocket. SM

I am aware of two programs involved in identifying and tracking near earth asteroids. The NASA and JPL joint program is called Near-Earth Asteroid Tracking project, and the Planetory Society (co-founded by Carl Sagan) funds small grants to amateur observers. I think that there are several other agencies, world wide, that are involved in finding dangerous asteroids. There are various plans for dealing with a potential threat, but I don't think anything has been funded or even seriously considered. SM

John, I was thinking much more local in that in the US the problem was popularized by the effects of acidification on the ecology, especially lakes. Otherwise I agree. SM

Michel, I wrote the post from general knowledge probably acquired from reading Science News for 40 years. The human bottleneck idea has been invoked often to explain rapid changes in humans evolution. Here is an older full text article on this topic-- http://mbe.oxfordjournals.org/content/17/1/2.full . It actually does not support a bottle neck in recent human evolution because the authors claim that the evidence isn't adequate. More important, it has extensive cited references, and you can always go to Google Scholar to search for more recent publications that cite this article to follow up if you have access to a university library (I really miss this). I suspect that this might be a minor controversy in the area of human evolution. I would appreciate any further information you find. Tony, I am also not an expert, but I did have an anthropology minor in undergrad, took a Ph.D. level behavioral genetics course (in 1976), and did some evolutionary research on a cave animal as a part of a nervous system development project. I think my information is correct, but as I said, see what you can find on the Genetics section of this forum. On your own I suggest "regression to the mean" as a starting search term. As a general recommendation I would like to encourage the idea of helping insure that all women have reproductive and other rights, families can depend on security from violence, and there is adequate employment to support families. This and a little education is what reliably brings reproductive rates down to sustainable levels. If this doesn't happen I think that the billions of new people that resulted from the green revolution are going to die horribly and create a bottle neck in human evolution. SM

Cap'n, thanks. This is really fun. I had been thinking about it starting with my super cannon on top of mount Everest (and no air resistance). A low power shot makes too small an orbit so the projectile hits the earth. With just the right increased velocity the projectile hits me in the back. So the velocity had to increase. An even higher velocity makes an elliptical orbit, but my error was assuming the mean velocity over the orbit was greater, forgetting that gravity decreases with distance, and not taking into account the energy required just to increase the altitude of the projectile. SM

Cap'n, it would help me to understand if you would label the variables in the formulas. SM

I think there is confusion here between the velocity of an orbiting object and the orbital period. An object in a higher orbit than another orbiting object (farther from the earth) will have a larger orbital period (take longer to complete an orbit) and will also have a higher velocity. SM

Scilearner, I don't understand your question. The orientation of somatotopic representations are arbitrary. They just have to be internally consistent. Shaft21, there are plenty of axons in the gray matter region of cerebral cortex. The axons of the neuron cell bodies there either travel locally, within the gray matter to make local connections, or exit into the white matter of cortex for traveling over longer distances. There are, however, no neuron cell bodies in the white matter. SM

John, gosh, what do you think the motivation was for putting on scrubbers? The point is that the problem has been reduced and that is why it is not so important, not just some changing political agenda. Here is a link regarding the successful cap and trade system that is in the Clean Air Act and supervised by the EPA. http://www.epa.gov/air/caa/peg/acidrain.html Your government at work! SM

Tony McC. You should post this in the Genetics section if you want a more technical answer, but I will expand on my previous comments: 1) The deal is that you and I don't know (nor does anyone else) if the groups of people who are producing many children are any less intelligent than the ones that have smaller families. I am referring here to the genetic portion of intelligence (native intelligence). One hundred plus years ago the US population was mostly rural and large families were very common. Do you think that their progeny (that be us) suddenly increased their native intelligence as family sizes decreased? Remember that the current concept of intelligence involves testing (e.g. IQ), but the tests require acquired knowledge. Someone with high native intelligence raised in a humble environment would probably go on to act like his peers and raise a large family and wouldn’t test very high. 2) A polygenetic trait involves many different genes, probably in specific combinations, to generate somebody who has a high native intelligence. Similarly, intelligence involves a whole array of behavioral traits. Something this complicated requires much more time to evolve, especially if there is any mixing of genes between different groups. If two geniuses produce a child, he/she is very unlikely to be a genius. Similarly, two retardates are very likely to have a child of normal intelligence. If the eugenics movement were to raise its ugly head again and take control of the government, with extensive testing and a precise breeding program, they might raise the intelligence of our nation, a little, in 1K to 2K years. And, there would not be any assurance that these folks would meet our approval of intelligence. With gene mixing between groups and no specific selection, a change may not happen at all. It would take a series of genetic bottlenecks with small founding populations to increase the rate of evolution, as has apparently happened in human evolution in the past, and this could happen again if our many billions of people were abruptly reduced down to a few hundred thousand survivors. 3) I think this point was pretty clear. It doesn't matter whether the folks with low socioeconomic status and large families are in our developed nation, or in an undeveloped nation. The selection pressure for intelligence would be stronger in the low socioeconomic group than in the high socioeconomic group. However, as mentioned above, this sort of weak selection pressure in large populations would only cause change at a pace that is not even worth considering in our rapidly changing world. In short, this is not a problem. SM

Juryoku, in terms of how evolution works your assessment is right on. Evolution works at the individual level. If homosexuality was a really important negative factor for evolution it would have been selected out. The fact that it remains means that this propensity has an important evolutionary function, or that it is not important to the evolutionary process at all and crops up occasionally, or that it is a pleiotropic trait that is not as important as its other genetic traits. The latter is unlikely because homosexuality, if it is a genetic effect at all, is probably a large multigene trait. SM

Yes Pippo, pop culture. Everybody with a viewpoint is trying to use word usage to bias their own issues. While you are at it, don't forget to add Frank Luntz, the conservative image manager of the Bush administration, who specifically and publicly (after his memo was outed and he was interviewed about it) told anti science politicians to always use say "climate change." He has since changed his tune. In case you haven't noticed, this is a science forum, and the climate scientists use warming versus change as is appropriate, or don't even make a distinction for current science. Do the words behind the IPCC acronym have any resonance with you. If you stick to the science, not what is in the political or blogosphere arenas, this is a non-issue. SM

Sound, I agree. I have not been active in neurophysiological research for more than 15 years, but a quick search revealed that in addition to retrograde action potentials invading dendrites there are a variety of neural systems that have retrograde axonal action potentials normally, and neurotransmitter release in a synapse from a postsynaptic cell to affect the presynaptic cell has been observed (retrograde synaptic transmission). I am glad that I put in the qualifier regarding evolution above. Amazing! SM

I think I was clear, but.... Just to be accurate, most action potentials are initiated in the axon hillock, not the cell body, and continue forward down the axon, and backward into the cell body. It gets even more complicated with dendrodendritic synapses. SM

TonyMcC, you don't have to worry too much about the greater number of offspring in the undeveloped nations or lower socioeconomic groups having an effect on the evolution of intelligence because of several factors. 1) Lower socioeconomic status/national development does not relate very well to innate (e.g. genetic) intelligence. 2) Intelligence is a very polygenetic trait and so is difficult to isolate by breeding. 3) It is modern developed nations that reduce evolutionary pressure so don't you think, in opposition to your concern, that being able to live long enough to breed and raise offspring in a challenging environment might instead provide a strong bias in evolutionary pressure for increased intelligence? Mrs Zeta, you seem to be supporting Lysenkoism. SM

On reading this I was interested in finding out what the difference in concordance is for monozygotic twins when reared together and reared apart. This difference would give more information than just MZ verses DZ twins. There is a huge Finnish study with more than 20K twins that has a good representation of twins reared apart, but I couldn't find anything not behind a paywall. There were a lot of references to studies involved in epigenetics, so maybe this is another avenue to look into. SM

Blahah your magical technofixes combined with Lemur's conservation might just get the developed nations through the crunch, although I would be interested on how we can economically recycle enough water for our (US) breadbasket when the Ogallala aquifer is used up. If everything continues as usual there will be 10 Billion people on the earth in 2050. This will be a time when fossil fuels costs will be skyrocketing and the oceans will be dying. We need fossil fuels to make fertilizer and the undeveloped nations will be starving because subsistence farming and the added stress of loss of food from the ocean will culminate in involuntary population control noted by Mr Skeptic. We all will get to spend our extra resources defending ourselves so that we can watch the gruesome die off live via satellite. SM

I don't think anybody has mentioned houseboats and floating homes. An example is in Seattle, but of course this is on a lake. Not having to deal with yard work and the ability to just tow your home to a different location to get away from an annoying neighbor is appealing. SM

The exterior of a cell is bathed in extracellular or tissue fluid. The interior of the endoplasmic reticulum and the Golgi apparatus is also referred to as the lumen. The topologic relationship is clear if one follows the contents and the inner leaflet of the ER traveling via vesicles to the Golgi, and then from the Golgi to the surface of the cell for exocytosis. Exocytosis puts the inner leaflet of the exocytic vesicle on the outside of the cell and the contents into extracellular space. Similarly, endocytosis makes intracellular vesicles that have the outer leaflet of the cell membrane as the inner leaflet of the vesicle. SM

Acid rain is less of an issue because it has been significantly mitigated in the US by a successful cap and trade scheme. I am not concerned about the terminology used for global warming, this issue is only important in popular culture. SM

Bmews, you are reporting your experiential perceptions regarding personnel interactions that, we all, males have to go through, but you are revealing this on a physics forum. Your actions are not appropriate. Suck it up and go on about your life. Make as good decisions as you can, and if they are actually good you will make it to where I am, much older, with a smile on my face. Really! Sm

Lemur, it sounds to me that you think that reproductive choice isn't an ethical decision in our current world. I made the choice to keep the number of my offspring to just replacement (one for each parents) 40 years ago with our second child just because of my concern for world population. This is really a moral choice and is the primary drive for all of our ecological problems. Those that don't understand need to be educated, the rest who ignore this, in my opinion, are just plain stupid. SM

Non-violent voluntary reproductive choice has nothing to do with your question. What is important is what is sustainable. The number of people on our earth that is sustainable requires a number of choices. Presumably we want a society that supports a scientific enterprise that is capable of continued progress (e.g. as suggested by Mrs Zeta) and allows for continuing improvement. On the debit side, most activities necessary to support society would have to be low enough as to be reasonably sustainable. For example, human wastes are currently causing major environmental problems. A population size that doesn't require any special solutions, such that all waste is handled by natural processes, would be appropriate. A similar analysis regarding energy needs and food production is necessary but my own, admittedly ignorant, suggestion is that we would have to reduce our current population of 7 billion down to about 1 billion or less. If you wish to deny my estimate, please explain where the fresh water, energy, fertilizer, and a replacement for foods supplied by the ocean are going to come from. If you agree, what is going to happen to the excess 6 billion humans? How are we going to deal with this? SM

Lemur. Land area for living space is not at all a factor in the overpopulation problem. What is important, as Ehrlich said 50 years ago, is resources. This includes energy, fertilizer for crops, fresh water for crops, and a healthy ocean. People who are educated enough to understand the problem and ignore it in their procreation decisions, in my opinion, are unethical. Please define paternalism in this context. SM

CharonY. I can't respond to your specific questions because I am having a problem understanding what you are saying relative to the previous posts. In my experience this means that we are both misunderstanding each other, so I will restate what I know in hopes that this will correspond to what you are about: Presynaptic neurons release a neurotransmitter onto postsynaptic neurons in a synapse. This results in transferring excitation, in the form of generating an action potential, from the pre- to postsynaptic neurons. This is a polarized event because a synapse usually only works in one direction (presynaptic neurotransmitter release and binding of the neurotransmitter to postsynaptic receptors). So, even though an axon is capable of transmitting an action potential in both directions the polarization of synapses in both upstream and downstream synapses insures that information, in the form of action potentials, is only transmitted in one direction. There may be instances in which antidromic action potentials in axons are normally used by the nervous system. I say this because I have given up trying to outguess the evolutionary process, but generally antidromic conduction mostly only occurs in the lab. I have recorded both extracellular and intracellular action potentials from neuron cell bodies when I have stimulated their axon, electrically, to generate antidromic conduction. SM