Cloning

A clone is any organism whose genetic information is identical to that of a "mother organism" from which it was created.

The the Asgard relied on cloning for millennia to perpetuate their species, eventually losing the ability for sexual reproduction. To preserve particular lives, a new body is cloned and the old consciousness is transferred into a new body. The technology for mind-transferal is unique to the Asgard. A cloned Asgard has a very primitive mind, until it receives a transferral.

However, this process ultimately doomed the Asgard species, as their cloned bodies were slowly but inexorably degenerating, eventually leading the Asgard to attempt to revert to an earlier stage of their development and regain the ability to reproduce sexually. This effort failed, eventually leading to the end of the Asgard species.