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Watsisname
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11 May 2017 15:33


I've been looking forward to this presentation, given today at CfA by Adam Riess, who won the Nobel Prize for the discovery that the universe's expansion is accelerating.  In this talk he discusses the latest work in measuring the Hubble constant with improved data sets and reduced uncertainties, which yield a greater value than that from the Planck-CMB results.  (I.e. the universe appears to be expanding a bit faster than we thought from Planck), and what the discrepancy between these results might mean for the Lambda-CDM model.

The Hubble constant remains one of the most important parameters in the cosmological model, setting the size and age scales of the Universe. Present uncertainties in the cosmological model including the nature of dark energy, the properties of neutrinos and the scale of departures from flat geometry can be constrained by measurements of the Hubble constant made to higher precision than was possible with the first generations of Hubble Telescope instruments. A streamlined distance ladder constructed from infrared observations of Cepheids and type Ia supernovae with ruthless attention paid to systematics now provide 2.4% precision and offer the means to do much better. By steadily improving the precision and accuracy of the Hubble constant, we now see evidence for significant deviations from the standard model, referred to as LambdaCDM, and thus the exciting chance, if true, of discovering new fundamental physics such as exotic dark energy, a new relativistic particle, or a small curvature to name a few possibilities. I will review recent and expected progress.
 
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17 May 2017 17:46

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams
 
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17 May 2017 20:27

Really enjoyed that one.  Great use of evolutionary principles, and it raises lots of very interesting questions of our future as an interplanetary species.  Or... lack of being a species.
 
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18 May 2017 06:41

But natural selection in a human population now only happens due to major genetic flaws.  He's assuming that Martian humans will have a very high mortality on Mars, probably more than what will be found acceptable for establishing a Martian colony.
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18 May 2017 08:53

I don't really agree with his assessment on Mars or branching species, at least not in the way he is presenting it.  Given the technological requirements for a sustainable colony and the space based economy required, it seems there would forever be swapping of humans between both planets preventing any real substantial speciation.

Seems more likely to me any changes in the species will be augmentation based instead of imposed by natural selection.
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18 May 2017 12:40

midtskogen wrote:
Source of the post humans will have a very high mortality on Mars

Agree!
For evolution to work you need natural selection, and for natural selection to work you need or many people death because of the innapropiate adaptation been pushed to the test or because some martians gain predominance in the population by reproducing more than others, much more.

For those tibetans that can breath in such low oxygenic conditions there have been probably thousands of deaths by suffocation or been unable to escape a not to much dangerous treat because of the unability to avoid it due to small reflexes in low oxigenic conditions.

If people on Mars develope resistance to radiation maybe it's because the shielding provided to the colony has leaks and because thousands of them die until a suffiently big population of radiation-resistance-humans has arisen.

Making people die to ensure adaptation to the martian enviroment would be the worst kind of Eugenics. When people started to die there would be an urge to return them to home.

Or maybe I'm exagerating and not considering very tiny undetectable evolutionary drifts due to very small problems that in the long run could accumulate to make this speciation possible, without a continuous generational high death toll. Maybe I'm wrong and not realizing the time-scale involved.



DoctorOfSpace wrote:
Source of the post it seems there would forever be swapping of humans between both planets preventing any real substantial speciation

Also agree with this.

The martian colonies would be extremely dependant of Earth resources even if in the end they could become self-sustained someway. Antartic scientific stations are totally dependant on the rest of the world, food, energy, water, construction materials, communications, etc... Mars would be the worst by many orders of magnitude. There would be a continuous exchange of material, and contact would be part of the rutine. I don't think that we would let them go untouched as if we where the polynesians and made an isolated society in the Eastern island and forget about them for tenths of thousands of years.

In fact I think that the capability on making such colonies would heavily relly on the capacity of working good communications and a very simple and inexpensive transit system beetween both planets in the first place.

Probably some isolation (like the south pole station when it gets in the cold months), but certainly not for more than two years each time (not enough to make their inmune system go unadapted for sure). Maybe if Mars was a planet like Earth it would be possible to send humans there and left them creating a society by their own before we could develope a frequent transport system.


I think my english is getting worse for some reason. I have to sleep more often.
 
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18 May 2017 15:58

I agree with Doc's questioning of whether Earth and Mars would really be sufficiently genetically isolated, but Midstkogen and FFT, I think you are misunderstanding the timescales and principles of selection effects and genetic drift that are operating here.

Certainly, if the selection pressures are very strong, with a high mortality rate for those with certain traits, then evolution will be very fast and within just a few generations there will be a significant shift in the gene pool.  This would be an unfavorable scenario.  But that is not what is being assumed here. Evolution does not require that the individuals notice the selection pressures or suffer high mortality rates.  

Consider the Tibetans.  They did not evolve to cope better with high altitude by dying much more often (even if they probably did die more often).  They adapted because individuals who had traits that made them marginally less likely to die were marginally more likely to propagate those traits to the next generation.  The difference in likelihood of dying from high altitude related causes from one individual to another is very small, and essentially unnoticeable compared to all sorts of other things that can cause you to die that do not relate to this selection pressure.  But over many generations, that small selection pressure leads to large change in the population.

For another example, consider evolution of the blind cavefish.  Do you think the fish that had more complete eyes experienced much higher mortality rates?  Well, you might calculate the energy cost of having functioning eyes and conclude that not having eyes saves the fish about 15% of its energy use.  That's pretty significant.  15% more energy demand for something that provides zero benefit.  A blind fish would have significantly higher survival rate than one with functioning eyes in that environment.

However, the loss of eyes did not happen in one step over a single generation.  It happened in a lot of very tiny steps over many generations.  Individuals with slightly less complex eyes had a slightly better chance of passing on those genes.  At the same time, since vision was not being selected for, the genes responsible for it were replaced through the slow genetic drift by random mutation, and some of those mutations may have enhanced other senses and in turn be selected for.

On a Mars colony we may imagine selection pressures for skin tone, bone density, height, ability to birth children without complications, and all sorts of things related to the differences between the Martian environment and the Earth.  But the selection itself may be subtle enough, due to such small differences at first between colonists and new arrivals, that they are not noticed.  But over time, these differences will accumulate, and new arrivals will look quite different from Martian families that lived there for hundreds or thousands of generations.

How quickly, if at all, the speciation between Earth and Mars occurs depends on a combination of how strong the selection pressures are and how well mixed the gene pool between the two planets is.  Technology and excellent health care can reduce the selection pressure, but never eliminate it, and how genetically isolated the populations are depends on the rate of migration between the two by ship traffic.
 
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18 May 2017 16:43

Watsisname wrote:
Source of the post How quickly, if at all, the speciation between Earth and Mars occurs depends on a combination of how strong the selection pressures are and how well mixed the gene pool between the two planets is.  Technology and excellent health care can reduce the selection pressure, but never eliminate it, and how genetically isolated the populations are depends on the rate of migration between the two by ship traffic.


If we get to a point of colonizing the solar system, given the current advances in genetic engineering, it seems likely people will be able to adjust their own genomes specifically for whatever environment they choose to live in, and if that is not possible then mechanical devices could supplement those deficiencies.  

I just don't see natural selection playing any key role in determining future humans given current and future technologies, any of those deviations mentioned in the video would be prescreened long before birth and either amplified by choice or removed. Given the fact that humans like to have human babies it seems likely traits that most resemble the parents and are non detrimental would be chosen, things like intelligence, strength, lack of disease, think more along the lines of improving what it means to be human without radically altering humans. Given modern medicine and what future medicine will be able to do, the selection pressure will be negligible at best.
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19 May 2017 00:21

Watsisname wrote:
Source of the post Consider the Tibetans.  They did not evolve to cope better with high altitude by dying much more often (even if they probably did die more often).  They adapted because individuals who had traits that made them marginally less likely to die were marginally more likely to propagate those traits to the next generation.

That evolutional change didn't require an increased mortality rate.  Remember that until a few generations ago, most humans born never reached reproductive age, about half never even reached the age of 5. Historically the rules have been quite different, so you can't really compare with processes governed by so different rules.  Does low mortality just mean that evolutional adaption will just take longer time, because it's so rare that a new genetic trait will actually matter?  I don't think it's that simple.
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19 May 2017 01:08

@Doc:  Actually I think proposing that humans in the interplanetary age choose their own genome will lead to faster speciation.

Species are like languages.  Once populations are separated, the languages begin to diverge without people really noticing it as it happens.  Then you compare them several generations later and notice how different they have become.  If people choose to modify their own genome for the environments they live in, then the gene pool changes more rapidly than nature would have it happen by random mutation, and then you'll get more genetically divergent populations more quickly.

Natural selection still applies in this case.  It is almost a tautology associated with being a living thing.  A truth that is true by definition.  "The genes of those who have more offspring that survive to adulthood become more prevalent in later generations."   

Even if parents ensure their daughters are genetically identical to the mother, and sons identical to the father, there will still be evolution, because people have psychology and your genes play a role in how you choose your mate.  There is a sexual selection pressure.

You also cannot know every factor for how your genes will affect your number of offspring relative to someone else. The relationship between the two is buried under complexity and situational circumstances, and environmental randomness.  Natural selection is often indistinguishable from random accident on the individual level, because what is being selected is a tiny and usually unnoticed difference in gene expression, with a tiny statistical difference in survival/reproduction probability.

Midtskogen wrote:
Historically the rules have been quite different, so you can't really compare with processes governed by so different rules.  Does low mortality just mean that evolutional adaption will just take longer time, because it's so rare that a new genetic trait will actually matter?  I don't think it's that simple.



The underlying rules are the same.  If there is a mechanism that selects for certain traits, those traits become more prevalent with time.  If there are traits that are selected against, or not selected for as frequently as other traits, they become less prevalent.  The rate of this change depends on the reproduction rate and the severity of the selection pressures.  There can be situations where the selection pressures are obvious (e.g. the infamous Peppered Moth example), but often they are subtle and take a very long time to produce a big change (e.g. the blind cavefish).
 
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19 May 2017 06:17

Watsisname wrote:
Source of the post The underlying rules are the same.  If there is a mechanism that selects for certain traits, those traits become more prevalent with time.

Evolution continues, but the question is to what degree the natural environment will direct what the selectable traits are.
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26 May 2017 17:22

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams
 
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07 Jun 2017 15:11

"Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams
 
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14 Jun 2017 03:06

I've recently found a channel that has very little views and subscribers but it should be in the top.
It's called Parallaxicality.

Their series about Planet X (nothing to do with the planet X myth at all by the way) are just awesome, he explains the nice model and the jumping jupiter scenario, the entire history of the IAU decission to degrade Pluto from the planetary club and all the evidence in favor and against Planet 9. I reccomend this series particularly.

 
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14 Jun 2017 04:05

These are outstanding!

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