It's thought that the collision resulted in a larger metal core, increasing the strength of our magnetosphere and thus our protection from ionized solar particl

It's thought that the collision resulted in a larger metal core, increasing the strength of our magnetosphere and thus our protection from ionized solar particles. As well, the moon slows our rotation and evens out the procession of our axis, which results in milder seasonal climate changes. The moon also caused tides which increased the environmental pressures on water-based life forms living in tidal pools to evolve to live amphibiously.