This will not be nearly as long as some other things on this site, but it may be way more important.
Humans are here because of evolution. This is not my point here, it's a premise we need to move forward. All the evidence points to the origin of people through natural selection and random mutations. Humans obey the laws of physics. They're complex structures made of molecules (which are made of elemental particles), but that doesn't exclude them from anything. There are no laws of physics that apply only to humans. As such, there are no "inherent" moral rules etc. The universe is indifferent to us.
There are two major direct consequences:
1) Anything spiritual is to be taken with much caution. Spirituality by definition requires some special rules for life. This would have to take some very concrete and arbitrary form to work properly. This has a plus side - we're alone. No deity bosses us around. After all, freedom is quite cool.
2) We're essentially messing up the system. Humans do what some players do in games - they look for exploits in the system that simplify their lives. That's why people build insane things in Dwarf Fortress (like automatic cleaning systems using aquifers). Abusing game mechanics can be very fun - for proof, see these videos from Kerbal Space Program by Danny2462. It's what allows progress in our world. And to properly abuse the rules, we must first know them. So we should probably get to work on that.
That's it. Think about that when you hear somebody talking about "something up there" or any variation on "soul".