Super ice age 'gave evolution a kick-start'

The appearance of the Earth's first multicelled organisms – which ultimately gave rise to humans – may have been triggered by the end of a super ice age in which the planet was a "snowball" for millions of years, scientists say.

The appearance of the Earth's first multicelled organisms – which ultimately gave rise to humans – may have been triggered by the end of a super ice age in which the planet was a "snowball" for millions of years, scientists say.

The "snowball" theory suggests that about 750 million years ago the Earth was covered with ice up to a kilometre thick, even in what are now the tropics. By comparison, the last ice age, which ended 10,000 years ago, glaciers reached only as far south as where New York is today.

Over the next 140 million years the temperature swung between freezing and heatwaves about four times – creating the opportunity for new organisms to evolve as nutrient-rich oceans were uncovered by retreating ice.

Evidence suggests it was only after this "snowball" period that multicelled organisms appeared. The oldest such fossils, called Ediacarans, have been dated to the same time as the "snowball" period ended.

The end of this ice age could have been the ideal opportunity for an explosion of new life, Andy Knoll, a palaeontologist from Harvard University, told New Scientist magazine. At such times, "you don't have to be good to win the game of evolution, you only have to be better than the other players", he said.