on the lack of a Neanderthal Y chromosome in modern humans [possibly musings 1a and 1b because I can’t help but digress]
I always love to throw our out of Africa origins at racists; the information from the article below [1] makes our human African-ness even more to be relished. To think that the allegedly more primitive Neanderthals were the first into Europe – home of civilisation, so the oft quoted Social Darwinist trope goes – and the allegedly superior Homo sapiens hung around in deepest darkest Africa more than a couple of hundred thousand years longer is a hoot.
‘Neanderthals and modern humans went their separate ways somewhere between 550,000 and 765,000 years ago in Africa, when Neanderthals wandered off into Europe but our ancestors stayed put. They would not meet again until Homo sapiens migrated into Europe and Asia between 40,000 and 50,000 years ago.
Scientists have recovered copies of the full male and female Neanderthal genomes, thanks to DNA from well-preserved bones and teeth of Neanderthal individuals in Europe and Asia. Unsurprisingly, the Neanderthal genome was very similar to ours, containing about 20,000 genes bundled into 23 chromosomes.
Like us, they had two copies of 22 of those chromosomes (one from each parent), and also a pair of sex chromosomes. Females had two X chromosomes, while males had one X and one Y.
Y chromosomes are hard to sequence because they contain a lot of repetitive “junk” DNA [1a], so the Neanderthal Y genome has only been partially sequenced[1]. However, the large chunk that has been sequenced contains versions of several of the same genes that are in the modern human Y chromosome[2].’
Yet, …‘many mysteries still surround the issue of what noncoding DNA is, and whether it really is worthless junk or something more. Portions of it, at least, have turned out to be vitally important biologically. But even beyond the question of its functionality (or lack of it), researchers are beginning to appreciate how noncoding DNA can be a genetic resource for cells and a nursery where new genes can evolve.
“Slowly, slowly, slowly, the terminology of ‘junk DNA’ [has] started to die[3],” said Cristina Sisu, a geneticist at Brunel University London…’ [See The Complex Truth about ‘Junk DNA’]
[1a] That the very male Y chromosome – the one that defines the male – is full of “junk” DNA, is amusing, n’est ce pas?
[1] From Modern human DNA contains bits from all over the Neanderthal genome – except the Y chromosome. What happened? – By Jenny Grave, Prof of Genetics, LaTrobe University, Published: June 17, 2024
[2] Note that ‘The human genome has three billion base pairs in its DNA, but only about 2% of them encode proteins. The rest seems like pointless bloat, a profusion of sequence duplications and genomic dead ends often labeled “junk DNA. {emphasis mine}” This stunningly thriftless allocation of genetic material isn’t limited to humans: Even many bacteria seem to devote 20% of their genome to noncoding filler.’ [Buehler J, The Complex Truth about ‘Junk DNA’.]
[3] So are males as useless – or “junk” riddled – as my 1a aside above implied?
Re “Junk” DNA: ‘The total DNA sequence is made up of base pairs, but not all sequences of base pairs serve the same function. Not all parts of the DNA sequence directly code for protein. Base pair sequences within DNA can be split into exons, sequences that directly code for proteins, and introns, sequences that do not directly code for a specific protein. The exon portion of our genome is collectively called the exome, and accounts for only about 1% of our total DNA. Exons and introns together form genes, sequences that code for a protein. On average there are 8.8 exons and 7.8 introns in each gene. The noncoding, or intron, parts of DNA used to be called “junk DNA,” random or repeating sequences that did not seem to code for anything. Recent research has shown that the majority of the genome does serve a function even if not coding for protein synthesis. These intron sequences can help regulate when genes are turned on or off, control how DNA winds itself to form chromosomes, be remnant clues of an organism’s evolutionary history, or serve other noncoding functions. [From Ancient DNA and Neanderthals.]
Remember these are musings, not in any way answers.
Inkstained fingers 