We think we know that our minds are products of natural selection.
If so, then our minds are merely evolved adaptations selected because they were associated with differentially-higher reproductive success.
But a mind which is merely a consequence of natural selection to increase differential reproductive success, is not a mind selected to apprehend objectively true knowledge about the world.
Therefore, since it is a product of the human mind, which is not selected to know objective truth but merely to enhance reproductive success; knowledge of natural selection cannot be regarded as objectively true.
We do not know that our minds are products of natural selection.