Evidence for a recent origin of penguins.

Penguins are a remarkable group of birds, with the 18 extant species living in diverse climatic zones from the tropics to Antarctica. The timing of the origin of these extant penguins remains controversial. Previous studies based on DNA sequences and fossil records have suggested widely differing times for the origin of the group.

Evidence that replication-associated mutation alone does not explain between-chromosome differences in substitution rates.

Since Haldane first noticed an excess of paternally derived mutations, it has been considered that most mutations derive from errors during germ line replication. Miyata et al. (1987) proposed that differences in the rate of neutral evolution on X, Y, and autosome can be employed to measure the extent of this male bias.