Gene origin timing. Timing of gene origin is assessed by determining the one-to-one orthologs between human and nine species listed on the left side of the figure. The species belong to Euarchontoglire (Primates and rodents), Xenarthra (Armadillo), Afrotheria (elephant and tenrec), Marsupial and Monotreme (opossum and platypus). Time of species divergence from the lineage leading to human is shown in MYA (million years ago). Filled squares represent the presence of the ortholog in the species. Numbers at the bottom of the figure denote the number of genes that display the presence/absence pattern across species.