When did human chromosome 2 fuse?(2023)
8 hours ago
- #chromosome fusion
- #human evolution
- #ancient DNA
- Human chromosome 2 resulted from the fusion of two ancestral chromosomes, reducing the chromosome count from 24 to 23 pairs.
- The fusion event likely occurred between 400,000 and 1.5 million years ago, possibly around 900,000 years ago.
- This fusion is shared by Neanderthals, Denisovans, and modern humans, indicating it happened in their common ancestor.
- The fusion site retains telomeric sequences and shows GC-biased substitution clusters, evidence of its ancestral telomeric origins.
- A population bottleneck around 800,000 to 900,000 years ago may coincide with the fixation of the chromosome 2 fusion.
- The deactivation of one centromere (2b) and retention of the other (2a) stabilized the newly fused chromosome.
- Chromosomal rearrangements like this can contribute to speciation but do not always prevent gene flow between species.
- Ancient DNA from other hominins could clarify whether species like Homo erectus also had the fused chromosome 2.
- The fusion may have had functional consequences or may have been fixed by genetic drift in a small ancestral population.