Human Evolution - the road to eusociality

Recent research in diffferent disciplins of science is coming together to illuminate the evolutionary steps leading to the human condition. The reason why the human condition is a singularity is simply the extreme improbability of all the preadaptations necessary for it to occur at all. Homo sapiens is the only species of large mammal - thus large enough to evolve a human-sized brain - to have made every one of the required lucky turns in the evolutionary maze.

• First preadaptation was the existence on land.
• Second preadaptation was a large body size.
  Large size and relative immobility that predetermined the trajectory of mammalian evolution, as distinct from that of social insects.
• Next preadaptation was the origin of grasping hands
  Specialisation of the early primates to life in trees (70 - 80 million years ago).
  Evolution of hands and feet build for grasping, particularly opposable thumbs and great toes.
  Evolution of larger brains as accomodation to the relativ complex feeding behaviour and to the three-dimensional and open vegitation of their habitat.
  Developed large eyes with color vision, placed forward on the head to give binocular vision and better sense of depth.
• Next preadaptation was Bipedalism
  When creatures evolved to live on ground, Bipedalism was adopted. Freeing hands and fingers from locomotion allowed prehumans to use them effectively in order to manipulate objects easily and skillfully.
  Following their divergence in evolution from the chimp line, the prehumans - now distinguishable as a group of species called the australopithecines - took the trend to bipedal walking much further. Their body as a whole was refashioned: Legs were lengthened and straightened; pelvis formed a shallow bowl.
  The body shed all of its hair and sweat glands were added everywhere allowing increased rapid cooling of the naked body surface.
  The forelimbs were redesigned for flexibility in the manipulation of objects and the arm became efficient in throwing objects (including stones and later spears to kill at distance).
• Next preadaptation was shift in diet
  A substantial amount of meat, either from scavenged carcasses (=Kadaver) of larger prey brought down by other predators or from live animals hunted and killed, has been included to the previously vegetarian diet. Meat yields higher energy per gram eaten than does vegetation.
• Next preadaptation was formation of highly organised groups
  The advantages of cooperation in the harvesting of meat led to the formation of societies as large as possible within the local environment, consisting of extended families but also adoptees and allies.
• Next preadaptation was control of fire
  About a million years ago the controlled use of fire became a unique hominid achievement. Such control of fire improved the yield for meat, allowing more animals to be flushed and trapped. Animals killed in the fire were also often cooked by it. (In later evolution, the mastication and physiology of digestion evolved for specialisation on cooked meat and vegetables. Cooking became a universal human trait and the sharing of cooked meals became a universal means of social bonding.)
• Next preadaptation was gathering at campsites (nests)
  With meat, fire and cooking, gatherings of groups at campsites that lastet more than a few days at the time were persistent enough to be guarded as a refuge. These groups were composed of extended families and also - if surviving hunter-gatherer societies serve as a guide - included outsider women obtained by exchange for exogamous marriage (exogamy = marrying outside of a specific cultural and biological group). Such a nest, as it can also be called, that they defended from enemies, has been the precursor to all other known animal species that achieved eusociality.
• Next preadaptation was division of labor
  The inevitable result energing quickly out of all these preadaptations was a complex division of labor.

By the time of Homo erectus, all of the steps that led this species to eusociality  - except the use of controlled fire - had also been followed by modern chimpanzees and bonobos. Thanks to our unique preadaptions, we were ready to leave these distant cousins far behind.

Only 10.000 years ago came the invention of agriculture, occuring at least eight times independently in the combined Old and New Worlds. Its adoption dramatically increased the food supply and, with it, the density of people on the land. This decisive advance unleashed exponential population growth and the conversion of most of the natural land environment into drastically simplified ecosystems.

(Edward O. Wilson, The social conquest of Earth)