A graphical representation of the standard human karyotype, including both the female (XX) and male (XY) sex chromosomes.

Why Do Humans Have 23 Pairs?

Other apes have 24 pairs. In our lineage, two chromosomes fused into chromosome 2.

Human Evolution: The Missing Chromosome

Two chimpanzees explore a rocky outdoor environment with lush greenery.

When It Happened

The fusion occurred during the split with the chimpanzee–bonobo line, leaving humans with 23 pairs.

Human Evolution: The Missing Chromosome

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