Fossil evidence suggests that ancestral penguins first appeared along the coasts of Antarctica and New Zealand about 65 million years ago. It is thought that they evolved from large sea birds, similar to the modern albatross; ancestral penguins apparently found that swimming and diving for their food was more efficient than flying. Likely resembling loons and cormorants in their earliest forms, penguins gradually lost their flight muscles and their wings regressed to shorter, more functional flippers; they also developed streamlined, fat-insulated bodies, equipping them for life in the sea.
When penguins first evolved, earth's climate was much warmer than it is today and there was no Antarctic glaciation. By the mid Eocene, 25 million years later, these marine birds had diversified, spreading northward to the South American coasts, to islands of the Indian Ocean, to southern Australia and to the southern coast of Africa. In the late Eocene and early Oligocene, a dramatic cooling of our planet's climate produced ice formation on Antarctica and forced penguin populations to adapt to local climate conditions. This broader range of regional climate led to the evolution of at least 40 penguin species by the Miocene Period (20 million years ago); seventeen species remain today, living in conditions ranging from the harsh, frozen world of Antarctica to the permanent summer of the Galapagos Islands.
