It has been believed that the asteroid strike that eliminated dinosaurs 65 million years ago led to the rise and diversification of mammals. But a

Figure 1: The echidna, one of the oldest mammals
Recall that the earlier expansion of dinosaurs themselves - after the Great Dying 250 million years ago - is another event where it's not quite clear whether the climate or a celestial body was responsible for the abrupt developments.













snail feedback (1) :
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