peter jay stein, md, ma
This 54 page synopsis of the evolution
of the Earth, the origin and progression of life, and the
emergence of humans as descendants of the hominin lineage, divides the last 4.57 billion years into progressively overlapping, imagistic, time segments, to outline our place in biological existence.
More than ninety-nine percent of all animal species that have ever lived are now extinct (Biology, 2015).
In contrast to the above 2012 source, geochemists more recently describe amphibilites, found also in Northern Canada, originally on the primal Earth's ocean floor, dated at 4.28 BYA. An iron-banded rock, called magnetite, also originally existing only on the ocean floor, also dates to 4.28 BYA, as does the 12 mile thick Earth's crust, and the oceans, themselves. It is remarkable that both crust and oceans existed already, within 300 million years of the Earth's birth, water droplets arriving within sodium chloride molecules, in turn existing within the meteorites bombarding the Earth, during hundreds of millions of years (Planet Earth: Birth of the Earth, youtube, 2014).
The oldest dated rock on Earth is 4.03 billion years old, that forms part of the Acasta gneisses of the Northwestern Canada Slace Craton. (Geologic Time Scale, 2012, p. 318)
adapted from multiple web sources - see bibliography)
There are an extimated 40 billion "goldilocks planets" within our galaxy alone, i.e., the Milky Way, that can sustain life, similar to life on Earth (from Crash Course, Big History: The Sun and the Earth, #3, youtube, 2014)
"Human evolution is Nature's experiment with versatility...Climate change seems to threaten our survival...but it may have held the keys...of how we became who we are...". Rick Potts, a specialist in sedimentology, theorizes that the variability, itself, of climate, was the driving force of human evolution, not the loss of forests, and theorized adaptation to the African savannah. Our ancestors adapted to change, itself, through versatility. The last 2 million years is characterized by climate instability, or as 'pulsating climate change' (PBS NOVA, Becoming Human, Episode # 1).
DNA, or deoxyribonucleic acid, the helical, double-stranded molecule that contains the codes for amino acid and protein synthesis that is the basis for heredity or genetic transmission, should actually be called DRNA, since the molecule is derived from its RNA, ribonucleic acid, ancestor. When an oxygen atom is removed from the sugar, ribose, to form "deoxy-ribose", RNA is transformed to DRNA, a conceptually clearer acronym than DNA (Peter Jay Stein, MD,MA, 2016).
Natural selection, the basis of evolution, occurs when random genetic copying errors generate mutations. Such mutations become physically or behaviorally (phenotypically) manifested as "traits", which then may be specifically "selected" by the very special environmental circumstances and demands that favor the survival of such traits. In summary, random mutations yield traits that are specifically selected (youtube: Crash Course: Evolution - The Ultimate Epic).
There are an estimated 200-400 species of living primates today, most adapted as tree-dwellers, but some, including humans, are ground-dwellers; of which about 85% are species of monkeys (Evolution, Roberts, A., 2011, p. 35; Essentials of Physical Anthropology, Jurmain, et al, 2016/2017, pp 137, 157).).
middle stone age:
~280,000 years ago to ~25,000 years ago
(industries appearing with the earliest anatomically modern humans)
280,000 years ago - blades
260,000 years ago - grindstones
240,000 years ago - pigment processing
240,000 years ago - pointed blades
140,000 years ago - burial rituals
130,000 years ago - shell fishing
120,000 years ago - long-distance exchange
100,000 years ago - fishing
80,000 years ago - bone tools
80,000 years ago - mining
80,000 years ago - barbed points
80,000 years ago - notation on stone
60,000 years ago - beads
40,000 - 60,000 years ago - images
Accompanying those milestones that have lead to the dominance of Homo sapiens, is the occurrence, accompanied by the growth of the neocortex, of
characterized by the increasing development of capacities for:
1) creating symbols: includes the creation of:
b)engraved and painted objects; and
2) planning for future action.
3) delay in gratification and impulse control.
5) flexible problem solving - ingenuity in:
a)complex and composite pre-shaped tool-making,
with greater hunting capacity;
b) fishing and trapping;
c) expanded social networking, with long-distance exchange of goods and ideas.
6) analogical/abstract reasoning.
prior to 300,000 years ago: rudimentary development of language and teaching?