How has your life been on this young planet?

For the first three billion years of life on Earth, the biosphere consisted of only single-celled organisms such as amoebas, paramecia, yeast, algae and bacteria. Six hundred million years ago individual cells began to enhance their survival by assembling into small colonial groups. Communal life offered two important survival advantages: 1) the collective “awareness” of communal cells offers greater survival opportunities over the limited awareness possessed by single, free-living cells; and 2) it is energetically more efficient to live in community…two can live as cheaply as one.

In cell communities consisting of small numbers of cells, each cell is able to effectively read and respond to environmental signals. However, in larger communities, cells in the middle of the crowd are unable to efficiently communicate with the prevailing external environment. This problem was resolved by creating a higher order of communal organization. Instead of each cell carrying out all of its own survival-requiring tasks, cells in larger cell communities became more efficient by expressing specialized functions.

Through the process of differentiation, specialized cell types such as skin cells, heart cells, bone cells, muscle cells and nerve cells, among others, evolved from common progenitor (ancestor) cells. Each cell type contributes a specialized service supporting the survival of the community. For example, nerve cells evolved to organize and coordinate the activities of the individual cells comprising the community. Nerve cells ‘read’ environmental signals, interpret them, select appropriate behaviors and then send behavioral directives to the cellular population.

While you might perceive of yourself as a single entity, in truth, you are a highly integrated organization of 50 trillion individual cells living in a bustling community beneath your skin. Your brain and nervous system represent a subset of cells whose function is to perceive and interpret environmental signals and then coordinate the functions of the body’s fifty trillion cells.