sethoflagos

Trillions of random experiments every second for a couple of hundred million years? Seems as good a way as any for turning the staggeringly improbable into practically a foregone conclusion. We see the evidence of this process all around us, And no evidence whatsoever for anything else.

Is this typically true for the UK? Examples of European outbreaks quoted by Wasiński B, Dutkiewicz J (2013). "Leptospirosis—current risk factors connected with human activity and the environment".Ann Agric Environ Med. 20) seem to correlate with periods of continuous high temperature (>18 C) coupled with high rainfall. This is situation normal for the tropics but not for the UK, If a cool night is enough to kill off any bacterium not kept warm by a mammalian body, then standing water is not going to remain infective for very long.

........you will feel absolutely elated to have survived it. Or totally unmoved because you're a bit of a psychopath. Or a bit guilty because you made it and others didn't. You won't know until you've been there. One thing is for sure. Tormenting yourself with the thought of the possibility is (I was about to say 'really stupid') irrational. It will happen one day, but maybe only once, and you may not be aware of it. If you are, the pain will probably be fleeting, followed by everlasting peace. Why spoil the precious time we all have between now and then worrying about an eventual certainty. Immortality probably gets a bit boring after a while anyway.

So Warp Factor 8 is a bit of a no go? Unless we travel into the void, which seems a bit pointless.

Your subconscious knows your deepest anxieties and will happily play them out for you under some (fortunately for me, fairly rare) circumstances. I've had a couple of serious scares in real life, but the adrenaline surge seems to focus you on how best to react (guess this probably varies by individual). Also I tend to get this strange curiosity for 'Ooh, I wonder what happens next'. But dreams can take all that precious control away from you (trying to run through a lake of bitumen springs to mind). Now it gets really scary!

This one has perplexed me for some time. Scenario: Travelling close to light speed towards say the Andromeda galaxy. If we were to look directly towards our destination, would we be totally frazzled by intensely blue-shifted radiation? (Assuming we didn't have a really good pair of Ray-Bans)

You are not being specific about what you mean by 'south' There are essentially two extremes to choose from: 1) Earth based, following a line of longitude. 2) Astronomically based eg following the stars as waypoints. Either way you will experience significant lateral forces (in the real world at least). In the earth based case, it is the coriolis 'force' (or rather 'effect') which manifests itself as an apparent acceleration westward as you move further away from the axis of rotation - hence the need for left rudder as mentioned by John Cuthber. In the astronomically based southern heading you will encounter an ever increasing sidewind tending to drive you eastwards from the air which is broadly coupled to the earth's rotation. You would need serious supersonic capability to beat that one.

Doesn't lightning cause water to dissociate into hydrogen and oxygen not by so much by electrolysis but by thermolysis? As I understand it, above 2000 C water starts splitting and by 3000 C over half of it is dissociated at equilibrium. So the 25,000+C core plasma temperature generated in the return stroke should easily be enough if only for a split second before it cools and the plasma recombines.

I'm quite familiar with solving systems such as the one I'm working on now, by numerical methods on computer (since the late '70s). That's bread and butter for some of the work I've done in the past, and indeed it is how I would normally have approached the system I'm currently working on. Pretty standard for hyperbolic PDEs. Clients pay for results in a cost-effective time-frame, not the beauty of the mathematics. But to have fully analytic solutions readily available to really quite complex systems is pretty mindblowing!

I found this paper quite fascinating. http://www.nature.com/articles/srep00263 Could competition for very rare and limited sources of biologically available molybdenum have put a serious restriction on multiple contenders for the first life, as this paper seems to infer?

Probably. The intention being to ensnare you in the logical paradox of stating that (for instance) human blood circulated in the veins of a non-human ancestor. And by recursive reasoning, that your non-human ancestor was therefore in fact human. And the house of cards comes tumbling down. It's a sad fact that for certain sections of society, there is little point in responding to such questions with logic and reason. Because your adversary (and it is an adversarial exchange) will not respect those rules. What is being exploited here, as mentioned by Phi for All, is the inherent logical weakness of the taxonomic system in handling a continuum of variation. If the question must be answered, maybe one strategy would be to reply that they were all simultaneously jury-rigged from the corresponding parts of the final missing link. It's a naughty argument. But it sidesteps the paradox, and they deserve no better.

It really depends on what you want to remember. If you want to improve your memory of names and faces, you practise strategies for learning how to associate names and faces - there are books on this sort of thing. If you want to learn how to commit long poems to memory, you start by memorising short poems, repeating them daily until they stick. Then gradually work up to longer poems. There are three golden rules to this sort of activity. 1) Don't waste time practising something that is of no direct use to you. Practise only what you want to be able to do. 2) Practising stuff you can do perfectly and practising stuff that is way in advance of your abilities are both a waste of time. 3) You have not completed mastery of a particular level until you can execute it perfectly. I suspect that practising remembering playing cards will only help you learn how to remember playing cards. If that's what you want to do, then joining a bridge club or a poker school may be more fun. I can remember card for card some bridge hands I played 30-odd years ago. Ask me my own telephone number and I've to look it up.

Isn't there some new thinking about the significance of pigmentation to dermal D3 synthesis? It's a moot point for us since childhood rickets remains fairly common in Nigeria and the Federal Government would very much like to eradicate it - the means and will are there. But the old assumption that it was due to low intake of dairy products seems to be questioned by work such as Signorello LB, Williams SM, Zheng W, Smith JR, Long J, Cai Q, Hargreaves MK, Hollis BW, Blot WJ (2010). "Blood vitamin D levels in relation to genetic estimation of African ancestry".Cancer Epidemiology, Biomarkers & Prevention.

This is all very good informative stuff CharonY. Going back to the OP, what struck me was an apparent underlying assumption that (and I paraphrase quite wildly here) 'If you come from the Albertine Rift your skin colour will be precisely RAL 8028 Terra Brown.' Now I know no one used those precise words, and yet there seems to be a great deal of resistance to any suggestion from me that there may well have been significant variance in the skin tone of our ancestors. Whether as much back then as there is in tropical Africa today, is neither here nor there.as far as I'm concerned. But any suggestion that there was zero or even insignificant variance smacks of a less than scientific agenda. As for the Bantu tribal group, yes I know a little, having been married to one for nearly 15 years. But then the Bantu expansion was a mere 3,000 years ago, coinciding with their discovery of iron smelting. Before that, their range was quite restricted. So extrapolating a stereotypically modern Bantu physiognomy back 200,000 years to being characteristic of all of humanity at that time seems a little far-fetched doesn't it? I know these visual arts people have to pick something to go on, but surely we realise that the artistic license here may well exceed the scientific justification. Or does it?

The point wasn't missed, it was ignored as (IMHO) non sequitur. Maybe a more constructive way of blowing my hypothesis out of the water would have been to refer me to something like 'Spectral Emissivity of Skin and Pericardium' (Steketee). From which I learn that the emissivities of pale and dark human skin in the mid-IR are not only equal, they are both phenomenally high. Much higher than water, higher even than black rubber and charcoal. Now that is food for thought!

For those interested in the depths of depravity from whence this abomination originates https://twitter.com/realityrandd http://www.realityrandd.com/

How about the example given for haplogroups L3, E, B from the National Geographic site on the human genome project. An Algerian subject which one would expect to be subject to very high incident levels of UVB.

I was fine with you up to this final point. But if moderate 'darkness' yielded sufficient advantage to balance African level UVB flux over the somewhat lower fluxes of elsewhere, then where is the driver for 'very dark'? 'Very dark' is at least in modern times a minority characteristic in Africa both locally and as a whole.

The fact that the male generative organ is particularly well designed for the removal of previously deposited fluids from the vicinity of the female generative organ is a pretty good guide to the comings and goings of our ancestors. Conspicuously different to the chimp strategy and seems weighted towards gaining maximum reproductive advantage from an infrequent opportunity. Make of that what you will. Mind you, the shenanigans that went on half a million years ago are not necessarily a good guide to current practice.

No matter had poorly you perform at any skill. if you practise it diligently in small increments, and demand perfection at each increment, you will gradually improve that skill. People typically fail to achieve this principally through two means: 1) They expect to achieve great advances with little work. 2) They prepare for failure with lame excuses, and then gladly accept the fulfilment of their expectation. Success requires a determination to succeed and a willingness to devote whatever time it takes to achieve that goal. Often that time can be measured in years.

Over the last few hours, I've been experimenting with the Wolfram free calculator. I hope you guys appreciate what a tremendous advantage this facility provides compared to what previous generations had access to. It solves in seconds stuff that used to take me weeks to work through by hand. But you know that don't you?

Why do you guys have so much difficulty in embracing the concept of multiple evolutionary drivers? There's no doubt that probably around the time we lost most of our body hair, MC1R became very strongly conserved under strong selective pressure to darken our pale ancestral (chimp-like) skin. There can be little doubt that the strong UVR protection provided by eumelanin producing melanocytes played a part in that. Possibly a dominant part. And it still remains highly conserved, almost invariant in most African populations. But there are a number of points to address here: 1) Active MC1R does not necessarily turn the individual jet black. It covers very nearly the whole gamut from a golden fawn upwards (and that's leaving aside albinism). This is at least partly under environmental control. 2) Susceptibility to mortality in adulthood from skin cancer has never seemed sufficiently strong a driver to explain the conservation of MC1R. The strength of that conservation has more than a hint that eg sexual selection played a role too. 3) You seem happy to accept the idea that MC1R ceases to be conserved (quite quickly apparently) in a slightly lower UV intense region as southern Asia, yet reluctant to acknowledge the many African populations, particularly those of Central and Western Africa where rain forest shielded them from UV far more effectively than a few degrees of northern latitude and for a considerably longer period of time without MC1R degradation. 4) And why doesn't MC1R reestablish its monopoly in high UV areas elsewhere in the world? 5) You can suspect the contrary as much as you like, but your utter dismissal of thermoregulation as a significant evolutionary player in the development of our species speaks volumes. Google 'cursorial hunting' then tell me that heat stress hasn't been a factor in who lived and who died.

Many thanks! I did eventually get some joy out of Wolfram, and the results actually simplify very nicely (or at least better than expected.) But it's good to have a longhand approach available for checking purposes. Seth

It's of the order 10W per degree difference between skin temperature and environment. The shade temperature typically for the African equatorial belt is rarely above 32 C. Usually a bit less. A resting human can typically get their metabolic thermal output down to around 70W. These ballpark figures indicate that radiative cooling could conceivably be a significant survival factor in a crisis. The skin pigment to emissivity relationship at the relevant frequencies (around 10 microns), I've no idea. I don't claim that it's the full picture, but I do see a certain amount of evidence around me and would be interested to see some proper research done on this. On an African population in particular. Rather than have it inferred from studies of other populations, which is what we see so often.

'There is no single gene for lighter skin' does not mean there are none, it means that there are many. I think you know this, The paper you quote does not deny it. And indeed goes on to state that that particular gene can only account for a fraction (27% was it?) of skin tone variation in European populations. So other controls must be involved, mustn't they? But we weren't discussing the skin tone of European populations were we? So I don't really see its relevance. Nor really do I see the point that you're trying to make with it. And when you say 'this particular gene........gives our skin its pigment', who exactly is the 'us'?