Answer: If we have lost seeds through the ages then they could not be reproduced, and we possibly would not know about them. Or we might find archaeological evidence, but no viable seed.
Loss of genetic diversity is a concern. There is actually a field called conservation genetics which addresses this type of question going forward.
Some seed savers also hope to prevent loss of seed strains and hope to maintain genetic diversity. Seed Savers Exchange for instance,
helps home gardeners participate. There are also government programs such as through the Fish and Wildlife Service.
You might also be interested in the activities of the Center for Plant Conservation and their resources.
I hope this helps answer your question.
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