Human existence

Human origins, and bipedality, dexterity and speech/song.  Bookmark and Share

You are your motor skills--from moving around, making things, and using breath to speak and sing. Paleoanthropologists have got them wrong. Your skill in them is due to a human specific ability to stabilize the position and kinetics of your body. This is unique to us because our large brains allow our movements to be fine-tuned by anticipatory adjustments. While scientists in each area have discovered this independently of each other, those studying our origins fail to appreciate its importance for why we exist. Here I explain the story.

Uniqueness

At first glance, we do not look unique compared to animals. Many animals stand on two legs, many make or use tools and are otherwise smart with their hands or their bills. Birds, of course, are rather good at singing. There are even parrots such as Irene Pepperberg's Alex that manage to say a few words.  But we are different--very different.

orangutan Casuarius casuarius
 chimpanzee hammering crow using tool bird singing alex [parrot
ALEX


Our uniqueness is due to an unique ability to stabilize our body
       upright human skeleton BIPEDALITY—we are the only animal that stabilizes our body as a column from head to ankle in vertical anatomical alignment. The weight of each body segment as a result is positioned over the next lower one. In normal standing, they are balanced. This requires lots of adjusting micro stabilizing movements.  In all other animals (including slightly in ostriches), limbs and body are bent so that body weight is held in tension by muscles—this allows for a much simpler means of keeping the body upright.
knapping DEXTERITY—we anticipatorily coordinate the actions of our two hands so they work together. The so-called nondominant one stabilizes  spatial location while the dominant one specializes in making stable but accurate kinetic force. For instance, stone tool knapping requires an exquisite stabilizing of the position of a core stone at the moment that a hammerstone (held by the dominant hand) impacts it to flake a chip. Bonobos have been taught to knap but this complex manual stabilization is beyond them.
human vocalization SPEECH/ SONG—birds sing with mini-breaths between their song notes. When we sing and speak, we string our vocalizations upon one single long outbreath. Hidden away, the pressure of our lungs below our vocal cords is exquisitely stabilized as it is released. No other animal including all birds can stabilizes in this way pulmonary pressure and the vocal track. Humans also do this while synchronizing such stabilized pressure with complex vocal track movements.
Our unique ability to stabilize our bodies is due to our large brains

human brain Such motor stabilization whether vertical body alignment, hand or lung and vocal tract synchronization exists due to us having big brains for our body size together with our long brain maturation. This allows us to acquire the internal models that enables motor control to constantly adjust our bodies against instability.


The abilities that create such enhanced skills also enable enlarged brains. This is due to a feedback in which they allow humans to engage in high-energy hunter-gathering and so provide the energy needed for bigger brains.

Outline of the main components of the proposed motor theory in the context of Homo origins. In the center of HUMAN UNIQUENESS is listed each of the major motor faculties: bipedality, dexterity and vocalization. To the left of them are the motor stabilizations that underlie their uniqueness, and to the right, the unique behavioral competence that they enable. To the right of HUMAN UNIQUENESS, lines connect behavioral competences to Homo ecological behavior in HIGH-ENERGY FOOD HUNTER-GATHERING. For example, the stabilization of anatomical vertical alignment bipedality allows efficient stance and walking, and so enables Homo to engage in long-distance travel. The three ecological behaviors are shown to act synergistically together with each other and also the social competences that derive from executive functions that also derive from INTERNAL MODELS (shown by a link running at the bottom). HIGH-ENERGY FOOD HUNTER-GATHERING is shown to link to PLEIOTROPIC SELECTION. The motor faculties are not concurrently done, and so permit the possibility of them relying upon shared neural resources (economies of scope). HIGH-ENERGY FOOD HUNTER-GATHERING also results in INCREASED FOOD PROVISION. This supports the prolonged nonadult stage of adolescence and increased encephalization and so EXPANDED CEREBELLO-CEREBRAL CIRCUITRY. This produces an increased capacity for INTERNAL MODELS and so the HUMAN UNIQUENESS.

Read the story in greater detail

Theory of human uniquenesss: Summary Uniqueness of human bipedality
Uniqueness of human song/speech
Uniqueness of human knapping/dexterity

Read the full Nature Precedings review pdf  comments subject to review can be put here. 

Related ideas upon bipedality

Human hand-walkers : five siblings who never stood up: pdf, and also in wikipedia  BBC film  and  Ulas family
Human balance, the evolution of bipedalism and dysequilibrium syndrome abstract  and pdf
Big heads, running and human evolution. Extract from Up from dragons: the origins of human intelligence (2002) McGraw-Hill with Sagan D. pdf
Powerpoint talk upon the origins of human bipedality and its link to balance. here

Related ideas upon song/speech

Song origins of language conference abstract here and Internet paper with Mario Vaneechoutte  here
Gesture, language origins, and right handedness here
Phones as a replication code for human vocalization here