I was thinking about stuff in general (which I do often.... even if it is rather dangerous... and illegal in some places....) and I decided that the thing that makes us human (and this is only ONE way to put it)... is that there are things that are more important than living.... or, to put it the other way around: There are things that are worth dying for. I think that that is what makes us different than other creatures... for them it's all about survival.
And I think it's when we lose that, then we become the most like animals. Morals leave... the good of others does not matter... we care only for life.... we cling to that.
From a biblical perspective, humans (and only humans) are made in the image of God... we reflect Him (though distorted it is by sin). So what did God do? Jesus, the "God-Man" came and died for us, taking our sin, so that we could live with God forever. God saw something worth dying for.
"Greater love has no one than this, that he lay down his life for his friends." -John 15:13
"This is how we know what love is: Jesus Christ laid down his life for us. And we ought to lay down our lives for our brothers." -1 John 3:16