The (In)Complete History of the Earth -

66 million years ago: Rise of Saurian civilisation.

65 million years ago: Total collapse of Saurian civilisation amid catastrophic scientific disasters, solar flares, and a largish asteroid. Surviving Saurians eventually become known as the 'Reptoids'. Also, extinction of most dinosaur species.

100 thousand years ago: Invasion of the 'Space Gods'. These extra-terrestrial divinities redesign certain advanced primates into modern humans.

80 thousand years ago: Rise of the 'Earth Gods'. These divinities contest the dominion of the Space Gods over the Earth.

80 to 60 thousand years ago: Battle rages between the two antagonistic divine factions. Humanity generally runs about bleating with terror.

60 thousand years ago: The Space Gods are defeated and driven from the Earth. They are reportedly unamused and lurk, hatefully, in the void.

60 to 25 thousand years ago: The terrestrial divinities rule the Earth... poorly. Some experiment with the creation/advancement of human civilisation, others gleefully rampage, unleash horrific monsters, and tutor humanity in the wonderful arts of mayhem and arguing (Ashermandrabaal insists that he was merely trying to instil a 'love of sportsmanship', but questions have been raised about his actions during this time).

25 thousand years ago: Rise of the proto-Atlantean civilisation.

1591 AD: Elgibigian observers first explore the Sol system.

1635 AD: Elgibigians establish a permanent observation post in the Sol system.

1741 AD: Total destruction of the Earth as a rogue planetoid slams into it. Humanity ignores this unfortunate event and is therefore unaffected. Reptoids without cover identities die horribly. The Elgibigian observers report this to the headquarters of the Galactic League before going utterly insane.

1741 AD to 1803 AD: The Galactic League collapses in a wave of insanity sparked off by the destruction of the Earth and the non-destruction of humanity.