Let's phrase it in another way: what is the meaning of rocks? How about the meaning of trees, or birds? Nothing, ostensibly. They just exist. Similarly, I think we take sentience to equal life in this regard, and what is the purpose of that? Nothing much, really. It's just a consequence of our predator/prey relationship with the rest of the world, now being applied to the ideals of civilization and human progress. That, in and of itself, is meaningless. We're a product of our environment, one of the great joys of human life is that you get to make up meaning for yourself. Some people ultimately aspire to be respected by their peers. Others find meaning in tending to the earth around us. There is no ground truth for the meaning of life though, I think that's silly.