The logic that Mars should have creatures doesn't make sense when comparing with Earth. Earth is closer to the Sun and receives more energy. Mars is smaller, less gravity, and receives less energy from the Sun. Gravity helps keep atmospheric particles near the planet. Mars has obvious problems supporting any kind of life. The atmosphere is too thin to support life as we know it. It's an apples to oranges comparison.
Natural selection does not apply to the tools creatures use like rocket ships or submarines.
Human beings are getting sicker much more from lazy lifestyles and poor diets.
An interesting observation is that wild plants tend to be hardier with more potency than cultivated, farm raised versions.