Complex sentence: Genes that promoted a capacity for symbolism may have been selected suggesting the foundations for symbolic culture may well be grounded in biology but behaviour that was mediated by symbolism may have only come later, even though this physical capacity was already in place much earlier.
Split into simpler sentences: Genes that promoted a capacity for symbolism may have been selected for, suggesting that the foundations for symbolic culture may well be grounded in biology. However, behavior that was mediated by symbolism may have only come later, even though this physical capacity was already in place much earlier.