This makes sense to our genetically savvy minds. We all know that genetically speaking, humans differ from a mushroom by only a certain combination of letters. But if you take this idea and put it into terms that speak closer to home like "nothing about being human is unique until after you leave your mother's womb", then maybe more thoughts would be provoked.
Its true (in case you even cared enough to think it wasn't), up until a point (A point not a single human can designate) we are no more unique in any physicality than your most rudimentary land crawler. the only time we gain the title of unique is when we start to stick "I" into the picture of the world by flexing our self-conscious muscle. But we have no idea when we are able to do this. There is no record of this change in or out of the embryo. We just couldn't then what seems by happenstance we knew we liked purple tootsie pops the most.
While with embryology we can trace with cut precision when our legs, mouth, brain etc begin to develop, there is still no way of tracing our consciousness. This is because consciousness still hasn't reached the level of cross-species commonality to be held eligible of the exclusive rank of embryo. Embryos are a secure path for change to make it into the next cut of reality, and it depends on each particular change's utility, paired with time, whether or not it makes the cut. It is needless to point how useful legs are, and even more so under this embryo-bouncer theory, as they are developed during an embryonic stage. Self-consciousness at the level of human is impossible to measure in any embryonic stage and as such it is possible to tell whether humans putting all their eggs into the mind basket during our trip down the path of evolution could be an action that ends dead.
There still hasn't been enough time to tell whether the human's mind; over the hawk's eye, or snake's tongue, or ant's sheer number - is the ticket to the next big show and while our narcissism can't imagine any other reality, the reality is that until our minds, as they stand today, are developed completely while as an embryo, we will never know for sure.