creatures are mecha

Evolution is a theory about replicators. Genes, not creatures, are replicators. Over billions of years replicators evolved the ability to build elaborate vehicles to assist in their replication i.e. complex bodies, and complex minds to auto-pilot them. In the case of humans the autopilot became too creative and flew the coop. 

A key dis-analogy is that mecha have designers, builders, and pilots, whereas genes are just designers and have to bake self-construction and autopilot into their designs. Also, creatures have moral significance (assuming they’re sentient) whereas genes do not (assuming they’re not).