The argument
"If we help animals that suffer in the wild, the weaker ones will survive and pass on their genes. The best-adapted genes would stop winning out, and that would be bad for future generations."
What "adapted" means
In evolution, being "adapted" means having traits that help pass genes on. It doesn't mean having a good life.
Adapted isn't the same as happy
Think back to the many-babies strategy. Having thousands or millions of babies is a great adaptation: it greatly increases the chance that the species keeps going. But it's terrible for the babies, because almost all of them die soon after birth.
On top of that, other traits that come along with the best-adapted ones can be harmful to those who have them.
Sometimes they line up
Of course, some traits help both with passing on genes and with having a better life. But that's a coincidence. Evolution doesn't "aim" at animals' well-being; it simply favors whatever reproduces more.
In short
- Being adapted means having a better chance of passing on genes, not having a good life.
- Many adaptations cause huge suffering, like having lots of babies.
- So the argument doesn't show that helping is wrong.