We feel obligated to show compassion towards other people, but this includes those who are not connected to us by tribe or community. This indicates our moral intuitions aren’t based on survival – ours or our group. Therefore, evolutionistic natural selection doesn’t explain the moral law.
You may argue that “moral” animal behavior, such as caring for young or helping members of a herd, is evidence that morality evolved in animals, and so could have evolved in us. But instincts in animals aid survival of their “family” or group. Besides, seemingly moral behavior in animals can alternatively be explained as “design features,” added to DNA as part of the design of life.