A 3D rendering of Luzio's skull.Credit: André Strauss
Posted on 08/04/2023 9:02:04 AM PDT by SunkenCiv
Luzio, a 10,000-year-old skeleton from São Paulo, Brazil, has some familiar-looking DNA.
He belongs to the same genetic population as all modern-day Indigenous peoples of the Americas...
Luzio was previously thought to have possibly belonged to a different, older, population, who settled in modern-day Brazil around 14,000 years ago...
“If there was another population here 30,000 years ago, it didn’t leave descendants among these groups.” [sic]
The researchers examined the genomes of 34 fossil samples, each at least 10,000 years old, from four different places on the Brazilian coast.
Luzio, among them, is the oldest human fossil found in São Paulo State. He’s named after Luzia, the 13,000-year-old female skeleton which is the oldest known in South America.
Some of the finds came from sambaquis, ancient Brazilian shell mounds...
The researchers believe that the mysterious disappearance of the sambaqui-builders can be attributed to a change in cultural practices, with fewer shell middens being constructed and more use of pottery.
(Excerpt) Read more at cosmosmagazine.com ...
A 3D rendering of Luzio's skull.Credit: André Strauss
“If there was another population here 30,000 years ago, it didn’t leave descendants among these groups.”
The same is true of at least 18 of each of our great-great-great-great-grandparents -- IOW, this doesn't show any such thing.
WHAT??????.........NOT CLIMATE CHANGE?????..............
Well, there was quite a bit of environmental change in that area in ancient times... most of the Amazon rainforest was at one point tilled farmland, until the civilization that lived there collapsed and the wilderness overtook it again.
Oooh, someone is gonna be in trouuuuble.
This is not a shock! modern man has been around a lot longer and in the New World for more than 10,000 years.
Why is this even a story?
Whoops.
The continuity of the DNA can only be proved or disproved if there’s DNA to compare.
Not exactly, chromosomes are not inherited intact, except for Y chromosomes. Genetic material swaps and splices. One chromosome can have genes from both mother and father.
That’s how some people have Neanderthal DNA.
No, that’s not how it happens at all.
We have 46 family trees. Half the 23 chromosome pairs come from each parent. There’s a tiny bit of mutation, there’s a tiny bit of gene-jumping, but these are of very low significance to the overwhelming stability of the inheritance process.
Each pair of grandparents do not contribute the same amount — the closest split would 12/11 or 11/12. Seven generations back, there are 64 great-great-great-great-grandparents, but only 46 chromosome halves to fell through to the next generation in each generation, so 18 of the g-g-g-g-grands don’t contribute anything to the current generation.
That doesn’t mean they’re not ancestors.
This is a great strength of sexual reproduction.
On paper, I know I’ve got common ancestors on both sides of my family. Thanks to DNA, I know I’m descended from my parents, and also know I didn’t get any matchy-matchy contributions from the common ancestors, because the parental DNA (that was passed to me anyway) isn’t identical on my chromosomes.
The fact that our Neandertal ancestors contribute as much as 3-4 percent (usually about 2-3 percent I think) means their chromosomes were a major source for all modern people, or it wouldn’t have persisted at the same percentage as each of our 4th-g-grands.
There are people around who think that chromosomes have ESP and play go fish with the genes to make sure those not yet conceived are exactly one quarter of each grandparent. Those people are nuts.
Look up genetic recombination or crossover.
The chromosome 3 that you give to your daughter is not likely to be the exact one you inherited from your father or your mother, but a mix of both.
https://en.wikipedia.org/wiki/Genetic_linkage
As I said, the genome is overwhelmingly stable, these swaps are very tiny in relation to the total, when they occur at all.
“The recombination frequency will be 50% when two genes are located on different chromosomes or when they are widely separated on the same chromosome. This is a consequence of independent assortment.”
Am I misunderstanding this? To me this means that alleles widely separated on the same parent chromosome are pretty likely to end up on separate although homologous chromosomes in the offspring.
Different wiki page:
“An exception is towards the end of meiosis, after crossing over has occurred, because sections of each sister chromatid may have been exchanged with corresponding sections of the homologous chromatids with which they are paired during meiosis. Homologous chromosomes might or might not be the same as each other because they derive from different parents.”
https://en.wikipedia.org/wiki/Sister_chromatids
At the beginning of that very page:
A sister chromatid refers to the identical copies (chromatids) formed by the DNA replication of a chromosome, with both copies joined together by a common centromere... A full set of sister chromatids is created during the synthesis (S) phase of interphase, when all the chromosomes in a cell are replicated. The two sister chromatids are separated from each other into two different cells during mitosis or during the second division of meiosis.
Compare sister chromatids to homologous chromosomes, which are the two different copies of a chromosome that diploid organisms (like humans) inherit, one from each parent. Sister chromatids are by and large identical (since they carry the same alleles, also called variants or versions, of genes) because they derive from one original chromosome. An exception is towards the end of meiosis, after crossing over has occurred, because sections of each sister chromatid may have been exchanged with corresponding sections of the homologous chromatids with which they are paired during meiosis. Homologous chromosomes might or might not be the same as each other because they derive from different parents.
There is evidence that, in some species, sister chromatids are the preferred template for DNA repair.
It happens, but it's rare. Get it?
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