Aliens, or even just an alien probe, could have visited Earth long ago and inserted a message into some ancestral creature.

外星人，或仅仅是一架外星探测器，可能在很久前已访问过地球，并在一些古生物中注入了讯息。

youdao

Many people believe space aliens have visited Earth in the past – if they’re not here right now.

许多人相信，外星人过去曾经造访过地球--即便他们目前不在地球上。

youdao

Many people believe space aliens have visited Earth in the past - if they're not here right now.

许多人相信，外星人过去曾经造访过地球——即便他们目前不在地球上。

youdao

Many people believe space aliens have visited Earth in the past - if they're not here right now.

许多人相信，外星人过去曾经造访过地球——即便他们目前不在地球上。

youdao