THE SURVIVAL OF THE FITTEST
Several contributors have misunderstood Darwin’s theory of the survival of the fittest. This is partly because the name of the theory is not well chosen. Any species that is fit enough to survive in all the circumstances in which it finds itself will survive. It does not need to be any fitter than that, let alone "fittest". Also there is not any universal connection between the survival of the species and the survival of the individual. Honey bees have had a good innings and yet 99.99% of them die off every winter. Fitness to survive does not necessarily involve aggression or ability to win fights. Not much is known about species before the days of the dinosaurs but the ones that are known to have survived since then are not all fierce of terrible; king crabs, wood lice, coelocanths.
If the population of any species becomes too large in its favourite habitat to be supported by the food available there will be competition for that food and the individuals least able to find or consume that food first will die off. But as soon as demand and supply stabilise, so will the species.
There are some species in which males compete to secure harems of females with whom to breed, and to drive away other males. No doubt the biggest and strongest males are most successful. But there is no such selection process in the females so the genetic pool will be fed by week, feeble, females as well as the big and strong males.
Among health freaks fitness is associated with strength, agility, stamina (and those with an axe to grind may add ruthlessness and sharp teeth and claws) but it is possible to survive without any of these though an unappetising appearance to possible predators may help. Alertness to danger, ability to hide, or camouflage, or wriggle into inaccessible crannies, are good survival techniques without any fitness in the health sense.
Natural disasters may wipe out any particular habitat and, with it, the species dependent thereon, which perhaps is why notable surviving species tend to be in the sea which is relatively immune to such disasters and always provides an escape route if, e.g. the temperature rises or falls unbearably over several millennia.
There is no necessary connection between aggression and survival. Homo Sapiens is one of the very few species with examples of such a connection.
Frank Walker