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Coincidently I've been reading and youtubing about human evolution recently. If anyone's interested here are some bullet point facts that may surprise other lay

by tombh 9y ago

Coincidently I've been reading and youtubing about human evolution recently. If anyone's interested here are some bullet point facts that may surprise other laymen. * In the last few years the Out Of Africa theory (modern humans originated solely in Africa) has received stiff competition from the Multi Regional theory. Namely that waves of human species have left Africa since we diverged from chimpanzees 4 million years ago and that our ancestors are from all the homo-inhabited regions of the world to a greater or lesser extent. * Neanderthals and Denisovans are 2 known species that certainly inhabited much of the world (apart from the Americas) from around 2/300,000 to 50,000 years ago. * We certainly bred with Neanderthals and Denisovans, some of us contain up to 4% of their DNA. * Mammals generally take about 5 million years before they evolve far enough to be reproductively isolated. Of course before then there can still be breeding problems, for which there is evidence of in our breeding with the aforementioned. * DNA from human skeletons several hunreds of thousands of years old can still be analysed. * Mitochondrial DNA is passed by mothers only and so undergoes very little mutation. So it provides a stable and valuable signature for detecting ancient affinities between species/sub-species. * By analysing the variation within genes certain characteristics can be interpreted like population size (eg; there were very few Denisovans) and that there are as yet unidentified species that humans have inherited from. * Neanderthals possessed the FOXP2 gene known to be central in human speech. * One of the oldest known oral traditions has evidence to verify a story from around 30,000 years ago: that Australian aboriginees brought the palm tree seeds with them from the north. See: http://www.abc.net.au/news/2015-04-03/aboriginal-legend-palm-tree-origin-central-australia-research/6369832 http://www.abc.net.au/news/2015-04-03/aboriginal-legend-palm... Forgive any errors in this amateur homework report.

detritus 9y ago
Wow. That last bullet point is particularly remarkable to me - both the implied level of 'technological understanding' and presumed foreplanning for significant journeys 30K years back and for the capacity of oral history to record what come today might not be the most pertinent information. Also quite amusing in the context of contemporary Australia's philosophy where alien plants and animals are concerned! :)
- yuchi 9y ago
  Citing that article: > “It suggests that Aboriginal oral traditions may have endured for up to 30,000 years, and lends further weight to the idea that some Aboriginal myths pertaining to gigantic animals may be authentic records of extinct megafauna” Wow ^ 2
  - pamqzl 9y ago
    I'm always extremely skeptical when someone suggests that oral traditions could possibly have survived for long periods of time. That's twelve hundred generations! Given what we know about the speed at which Chinese Whispers tend to drift, the idea that any story can last 1200 generations is an extraordinary claim that demands extraordinary proof. Hundreds of Aboriginal tribes had hundreds of contradictory myths on hundreds of subjects. Most of them are verifiably false (e.g. those rocks over there are not, in fact, the remains of three young women who got turned into stone for disobeying their father). Some of them are probably correct by complete accident. As for gigantic animals... well, they're a pretty common motif in myths and stories all around the world. Maybe it's some distant memory our cultures all have of the larger animals that used to live around here... or maybe it's just because giant animals are cool. In Aboriginal myths, giant animals are often really really giant, because they're used as explanations for geographic features -- e.g. rivers are caused by the meanderings of a giant snake.
    - micheljones 9y ago
      Some tribes in north of Australia have verifiable myths about the geography of the lands that have been under the sea off the north of Australia for 6-8 thousand years at least (meaning, the description of the land features matches the sea floor geography).
      - flukus 9y ago
        Has anyone quantified their myths properly? If not then they're just cherry picking.
tim333 9y ago
Minor correction - I think the chimp divergence was longer ago - Wikipedia: While "original divergence" between populations may have occurred as early as 13 million years ago (Miocene), hybridization may have been ongoing until as recent as 4 million years ago
- tombh 9y ago
  updated, thanks
evolve2017 9y ago
Very interesting! I'm not sure I agree with your reasoning for the mitochondrial mutation point: > * Mitochondrial DNA is passed by mothers only and so undergoes very little mutation It's true that mothers pass on mitochondrial DNA but this doesn't necessarily require the absence of mitochondrial DNA mutations. I would imagine the lower rates of DNA mutation are due to the importance of the mitochondrial genome for generating a cell's energy.
- gus_massa 9y ago
  The mutation rate of mitochondrial DNA is much faster than in nuclear DNA [1]. But mitochondrial DNA does not have crossover, so the mutation tree is much easier to build. [1] From: https://en.wikipedia.org/wiki/Mutation_rate#Variation_in_mutation_rates https://en.wikipedia.org/wiki/Mutation_rate#Variation_in_mut... > Human mitochondrial DNA has been estimated to have mutation rates of ~3× or ~2.7×10−5 per base per 20 year generation (depending on the method of estimation); these rates are considered to be significantly higher than rates of human genomic mutation at ~2.5×10−8 per base per generation. Using data available from whole genome sequencing, the human genome mutation rate is similarly estimated to be ~1.1×10−8 per site per generation.
  - anderspitman 9y ago
    Saw this after I posted.
- anderspitman 9y ago
  I would expect the mutation rates of mitochondrial and nuclear DNA to be about the same, unless the mitochondria have additional repair proteins not involved with nuclear DNA, or the shorter length of the mitochondrial chromosome affects the rates, or some other process I'm not familiar with. I think maybe parent meant to refer to diversity, not mutation. With nuclear DNA, the offspring chromosomes are made up from a combination of the parents' DNA. There's a lot of swapping and mixing and matching that takes place. This adds diversity to the population.
  - 9y ago
joshgel 9y ago
I'm reading the book Sapiens right now, which I highly recommend. Lots of interesting facts. But also a broad explanation of the theory of human development. Most interesting fact I learned: At one point there were as many as 6 human species (Homo sapiens, homo errectus, etc) on earth at the same time!
- raihansaputra 9y ago
  I really really recommend the sequel of Sapiens, Homo Deus. I can't really describe it in words.
rgrieselhuber 9y ago
Do you happen to have a good source handy on the growing acceptance of the Multi-Regional theory vs the Out of Africa theory? This is obviously a topic with political implications so looking for something that is accepted as a neutral source.
- danieltillett 9y ago
  It is not a case of one or the other, they are both right. All non-Africans are a hybrid between Africans and Neanderthals or Africans/Neanderthals/Denisovans. You are right that this topic is politically sensitive - so sensitive that the data is basically ignored outside of science.
  - nikcheerla 9y ago
    Why is it politically sensitive? I can't see any obvious political implications ...
    - tombh 9y ago
      I'm not an expert, so just guessing, but I imagine it's something similar to the whole Arian stuff from the Nazis, ie: "look, our genes are more closely related to the most 'original' and 'pure' human lineage".
- tombh 9y ago
  A lot of the Multi-regional stuff I learnt is from the University of California Youtube channel. There's a playlist here, it's quite big, but a lot of relevant videos are in there: https://www.youtube.com/watch?v=v0j77rODO3E&list=PL1B24EADC01219B23 https://www.youtube.com/watch?v=v0j77rODO3E&list=PL1B24EADC0...
danieltillett 9y ago
You missed what is probably the most important thing about human evolution and that is due to the rapid population rise after the invention of argriculture more human evolution has happened in the last 10,000 years than the previous million. The other is that human population is filled with new genes that are under positive selection which have only partially spread through the population. Humans are probably the worst species to study genetically as all the normal assumptions you need to make don't hold. One minor nitpick, your evidence of the oldest oral tradition is not very strong as there are only four major points on the compass. The likelihood of chance and cherry-picking is high.
- twelvechairs 9y ago
  > your evidence of the oldest oral tradition is not very strong as there are only four major points on the compass. The likelihood of chance and cherry-picking is high. I think the point is that the palms are introduced (not native) more than their cardinal direction (i dont believe they were using a western compass at the time so as to have four directions)
  - danieltillett 9y ago
    If you read the articles linked the evidence that this "knowledge" has been passed down for 30,000 years is not strong. Firstly, the palms are native to Australia, just other populations are found 1000 km to the north. Secondly, the palms have only being separated for 15,000 years at most. Thirdly, the northern evidence is actually "gods brought the palms from the north".
BurningFrog 9y ago
> We certainly bred with Neanderthals and Denisovans Another way of looking at it is that we are the Neanderthals and Denisovans. The Neanderthals population is estimated at 70,000 at their peak. At 2% of 7 billion, we Neanderthals are now two thousand times more plentiful!

by tombh 9y ago

detritus 9y ago

Wow. That last bullet point is particularly remarkable to me - both the implied level of 'technological understanding' and presumed foreplanning for significant journeys 30K years back and for the capacity of oral history to record what come today might not be the most pertinent information. Also quite amusing in the context of contemporary Australia's philosophy where alien plants and animals are concerned! :)

yuchi 9y ago
Citing that article: > “It suggests that Aboriginal oral traditions may have endured for up to 30,000 years, and lends further weight to the idea that some Aboriginal myths pertaining to gigantic animals may be authentic records of extinct megafauna” Wow ^ 2
- pamqzl 9y ago
  I'm always extremely skeptical when someone suggests that oral traditions could possibly have survived for long periods of time. That's twelve hundred generations! Given what we know about the speed at which Chinese Whispers tend to drift, the idea that any story can last 1200 generations is an extraordinary claim that demands extraordinary proof. Hundreds of Aboriginal tribes had hundreds of contradictory myths on hundreds of subjects. Most of them are verifiably false (e.g. those rocks over there are not, in fact, the remains of three young women who got turned into stone for disobeying their father). Some of them are probably correct by complete accident. As for gigantic animals... well, they're a pretty common motif in myths and stories all around the world. Maybe it's some distant memory our cultures all have of the larger animals that used to live around here... or maybe it's just because giant animals are cool. In Aboriginal myths, giant animals are often really really giant, because they're used as explanations for geographic features -- e.g. rivers are caused by the meanderings of a giant snake.
  - micheljones 9y ago
    Some tribes in north of Australia have verifiable myths about the geography of the lands that have been under the sea off the north of Australia for 6-8 thousand years at least (meaning, the description of the land features matches the sea floor geography).
    - flukus 9y ago
      Has anyone quantified their myths properly? If not then they're just cherry picking.

tim333 9y ago

Minor correction - I think the chimp divergence was longer ago - Wikipedia: While "original divergence" between populations may have occurred as early as 13 million years ago (Miocene), hybridization may have been ongoing until as recent as 4 million years ago

tombh 9y ago
updated, thanks

evolve2017 9y ago

Very interesting! I'm not sure I agree with your reasoning for the mitochondrial mutation point: > * Mitochondrial DNA is passed by mothers only and so undergoes very little mutation It's true that mothers pass on mitochondrial DNA but this doesn't necessarily require the absence of mitochondrial DNA mutations. I would imagine the lower rates of DNA mutation are due to the importance of the mitochondrial genome for generating a cell's energy.

gus_massa 9y ago
The mutation rate of mitochondrial DNA is much faster than in nuclear DNA [1]. But mitochondrial DNA does not have crossover, so the mutation tree is much easier to build. [1] From: https://en.wikipedia.org/wiki/Mutation_rate#Variation_in_mutation_rates https://en.wikipedia.org/wiki/Mutation_rate#Variation_in_mut... > Human mitochondrial DNA has been estimated to have mutation rates of ~3× or ~2.7×10−5 per base per 20 year generation (depending on the method of estimation); these rates are considered to be significantly higher than rates of human genomic mutation at ~2.5×10−8 per base per generation. Using data available from whole genome sequencing, the human genome mutation rate is similarly estimated to be ~1.1×10−8 per site per generation.
- anderspitman 9y ago
  Saw this after I posted.
anderspitman 9y ago
I would expect the mutation rates of mitochondrial and nuclear DNA to be about the same, unless the mitochondria have additional repair proteins not involved with nuclear DNA, or the shorter length of the mitochondrial chromosome affects the rates, or some other process I'm not familiar with. I think maybe parent meant to refer to diversity, not mutation. With nuclear DNA, the offspring chromosomes are made up from a combination of the parents' DNA. There's a lot of swapping and mixing and matching that takes place. This adds diversity to the population.
- 9y ago

joshgel 9y ago

I'm reading the book Sapiens right now, which I highly recommend. Lots of interesting facts. But also a broad explanation of the theory of human development. Most interesting fact I learned: At one point there were as many as 6 human species (Homo sapiens, homo errectus, etc) on earth at the same time!

raihansaputra 9y ago
I really really recommend the sequel of Sapiens, Homo Deus. I can't really describe it in words.

rgrieselhuber 9y ago

Do you happen to have a good source handy on the growing acceptance of the Multi-Regional theory vs the Out of Africa theory? This is obviously a topic with political implications so looking for something that is accepted as a neutral source.

danieltillett 9y ago
It is not a case of one or the other, they are both right. All non-Africans are a hybrid between Africans and Neanderthals or Africans/Neanderthals/Denisovans. You are right that this topic is politically sensitive - so sensitive that the data is basically ignored outside of science.
- nikcheerla 9y ago
  Why is it politically sensitive? I can't see any obvious political implications ...
  - tombh 9y ago
    I'm not an expert, so just guessing, but I imagine it's something similar to the whole Arian stuff from the Nazis, ie: "look, our genes are more closely related to the most 'original' and 'pure' human lineage".
tombh 9y ago
A lot of the Multi-regional stuff I learnt is from the University of California Youtube channel. There's a playlist here, it's quite big, but a lot of relevant videos are in there: https://www.youtube.com/watch?v=v0j77rODO3E&list=PL1B24EADC01219B23 https://www.youtube.com/watch?v=v0j77rODO3E&list=PL1B24EADC0...

danieltillett 9y ago

You missed what is probably the most important thing about human evolution and that is due to the rapid population rise after the invention of argriculture more human evolution has happened in the last 10,000 years than the previous million. The other is that human population is filled with new genes that are under positive selection which have only partially spread through the population. Humans are probably the worst species to study genetically as all the normal assumptions you need to make don't hold. One minor nitpick, your evidence of the oldest oral tradition is not very strong as there are only four major points on the compass. The likelihood of chance and cherry-picking is high.

twelvechairs 9y ago
> your evidence of the oldest oral tradition is not very strong as there are only four major points on the compass. The likelihood of chance and cherry-picking is high. I think the point is that the palms are introduced (not native) more than their cardinal direction (i dont believe they were using a western compass at the time so as to have four directions)
- danieltillett 9y ago
  If you read the articles linked the evidence that this "knowledge" has been passed down for 30,000 years is not strong. Firstly, the palms are native to Australia, just other populations are found 1000 km to the north. Secondly, the palms have only being separated for 15,000 years at most. Thirdly, the northern evidence is actually "gods brought the palms from the north".

BurningFrog 9y ago

> We certainly bred with Neanderthals and Denisovans Another way of looking at it is that we are the Neanderthals and Denisovans. The Neanderthals population is estimated at 70,000 at their peak. At 2% of 7 billion, we Neanderthals are now two thousand times more plentiful!