[quote=@FreeElk]
disproportioned eyes (which require much more energy for your body to keep going) and you end up forgetting to eat and starve.
[/quote]

(may be onto something there...)

Granted: in our haste to spread out into the cosmos, we forget to handle matters at home. Pollution, desertification, global warming and a multitude of other environmental disasters befall the Earth, destroying all our currently arable land. Starvation returns, and the population rapidly drops to below 20,000 off-world colonists. By the end of the 22nd century, these colonies have one by one fallen into varying states of disrepair/failure as the resources, as well as the knowledge, provided by the factories and schools of the Earth have all been depleted or forgotten. By the end of the 23rd century the last human life disappears when the lonely woman steps out into the cold vacuum of space before the last of the life support fails.

I wish the upcoming eclipse's totality would be observable from my town.