The human genome comprises a sequence of approximately 3 billion component parts, called nucleotides, which are organized into DNA molecules—the double helix. The nucleotides, which serve as the alphabet for the language of life, are represented by just four letters: A, C, G, and T, corresponding to adenine, cytosine, guanine, and thymine. The nucleotide alphabet codes for the sequence of amino acids the body will use to build proteins.

Combinations of three nucleotides indicate one of twenty possible amino acids (for example, CCT codes for the amino acid glycine), so sets of nucleotide triplets form the instructions that cells use to build proteins. These proteins perform the work of the cells from development throughout life, contributing to both our physical attributes and many of our less tangible features, such as behavior, learning, and predisposition to disease. A segment of a DNA molecule that codes for one complete protein is called a gene. The human genome is carried on 23 different chromosomes

There are several theories as to what humans all have in common. A popular example is that humans search for purpose, are curious and thrive on new information. High-level thought processes, such as  , and ,^]are considered to be defining features of what constitutes a It has been defined as humans' capacity for 'good' and 'evil'

The e D has identified what he refers to as the four "givens" or ultimate concerns of human existence - concerns with meaning, loneliness, freedom and mortality.Yalom argues with that man is "condemned to freedom", and must face his ultimate aloneness, the lack of any unquestionable ground of meaning, and ultimate mortality.

In most developed , improvements in technology,  , and  have brought about quantitative, not necessarily qualitative, marked changes in the human condition over the last few hundred years, with increases in and population (). One of the largest changes has been the availability of , which has changed the lives of countless humans. Even then, these changes only alter the details of the human condition.