You guys really don't understand:

What we think we should do is a product of cognition developed through an evolutionary process intended chiefly to help us propagate our genes.

This thread is just soaked with people who both overestimate human agency and cognition.

Humans are not magical. We are animals. Subject to the same processes as all others.

To think our ethically reasoning is anything other than a particularly complex permutation of our drive to propagate our genes is profoundly arrogant.

By the way, I'm not proposing this as a sound ethical model upon which to base one's life.

You have to understand: this itself isn't an ethical model. The ideal ethical model by implication, imo, is that which allows us the safest planet with bountiful food and stable social systems to raise our offspring in environments that give them the best shot at growing up and continuing the family line.