Some overlap with the 'vital illusion' thread here. You can go back more or less as far as you want and there's always someone lamenting the loss of authenticity and having departed some mythical golden age. I don't think it ever existed.
I was reading Nietzsches Uses and Abuses of History this a.m. and he was talking about how happy cows are how they have no sense of the past no sense of history they live in a perfect unselfconscious present which is to humanity as childhood is to adulthood
Perhaps there's something there but you also wonder how we could possibly know this about a cow, it seems like we just project onto animals the same way we in the West projected onto Polynesian islanders or any noble savage, we construct their identity by inverting ourselves, imposing our desires
There's a huge tradition in Western phil of saying that animals don't know they're going to die. But it seems to me like, in some sense, knowledge of your own mortality is the fundamental fact of biotic life. Your body has got to know it's possible just to stay alive. The entire nervous system is wired up to the possibility of death.
But also people talk about this in terms of human aging and lifespan. They talk about how teenagers brains aren't developed yet so they think they're invincible and can't be harmed.