A Potential Evolution of Human Brain Size
This essay examines the evolution of human brain size in relation to human species, brain volume, potential neurons, climate and time.
The ratio of these are then examined.
The potential influence of current climate change on human brain size is then extrapolated.
Historic Data
Species Sahelanthropus
Brain volume (ml) 320 to 380 ml
Potential Neurons 22,222,222,080
Climate Miocene
18 deg c temperature
Time 21 to 14 million years ago
Species Australopithecines
Brain volume (ml) 380 to 430 ml
Potential Neurons 26,388,888,720
Climate Pliocene to Pleistocene
19 deg c to 6 deg c
Time 5 to 1.8 million years ago
Species Homo Habilis
Brain volume (ml) 618 ml
Potential Neurons 42,916,666,392
Climate Pleistocene
11 deg c
Time 2.8 million years ago
Species Homo Erectus
Brain volume (ml) 850 ml
Potential Neurons 59,027,777,400
Climate Pleistocene
11 deg c
Time 1.9 million years ago
Species Homo Heidelbergensis
Brain volume (ml) 1100 to 1400 ml
Potential Neurons 76,388,888,400
Climate Pleistocene to present
11 deg c to 16 deg c
Time 600,000 to 400,000 years ago
Species Homo Neanderthalensis
Brain volume (ml) 1600 ml
Potential Neurons 111,111,110,400
Climate Pleistocene to present
11 deg c to 16 deg c
Time 300,000 to 28,000 years ago
Species Homo Denisovans
Brain volume (ml) 1200 to 1400 ml
Potential Neurons 83,333,332,800
Climate Pleistocene to present
11 deg c to 16 deg c
Time 250,000 to 40,000 years ago
Species Homo Floriensis
Brain volume (ml) 380 ml
Potential Neurons 26,388,888,720
Climate Pleistocene to present
11 deg c to 16 deg c
Time 94,000 to 12,000 years ago
Species Homo Sapiens
Brain volume (ml) 1440 ml
Potential Neurons 86,000,000,000 to 100,000,000,000.
1 ml to 69,444,444 neurons
Climate Pleistocene to present
11 deg c to 16 deg c
Time 195,000 years ago to current time
Ratios of Data
Total evolutionary time
= 21,000,000 years
Smallest brain size to largest brain size
= 320 ml to 1600 ml
= 1 to 5 ratio
Smallest brain size to current brain size
= 320 ml to 1440 ml
= 1 to 4.5 ratio
Largest brain size to current brain size
= 1600 ml to 1440 ml
= 1 to 0.9 ratio (decrease in size)
Brain size evolution ratio
= 320 ml to 380 ml
= 380 ml to 618 ml
= 618 ml to 850 ml
= 850 ml to 1100 ml
= 1100 ml to 1600 ml
= 1600 ml to 1200 ml Denisovan decrease
= 1200 ml to 380 ml Floriensis decrease
= 1600 ml to 1440 ml Neanderthalensis to Sapiens decrease
Potential brain neuron evolution ratio
= 22,222,222,080 to 26,388,888,720 = 1 to 1.2
= 26,388,888,720 to 42,916,666,392 = 1 to 1.6
= 42,916,666,392 to 59,027,777,400 = 1 to 1.4
= 59,027,777,400 to 76,388,888,400 = 1 to 1.3
= 76,388,888,400 to 111,111,110,400 = 1 to 1.5
= 111,111,110,400 to 83,333,332,800 = 1 to 0.75 Denisovan decrease
= 83,333,332,800 to 26,388,888,720 = 1 to 0.3 Floriensis decrease
= 111,111,110,400 to 100,000,000 = 1.1 to 1 Neanderthalensis to Sapiens decrease
Brain size evolutionary time periods
= 21,000,000 to 5,000,000 = 16,000,000 years
= 5,000,000 to 2,800,000 = 2,200,000 years
= 2,800,000 to 1,900,000 = 900,000 years
= 1,900,000 to 600,000 = 1,300,000 years
= 600,000 to 300,000 = 300,000 years
= 300,000 to 250,000 = 50,000 years
= 250,000 to 94,000 = 156,000 years
= 250,000 to 195,000 = 55,000 years
Temperature range changes
= 18 deg c to 6 deg c = 12 deg c decrease
= 6 deg c to 11 deg c = 5 deg c increase
= 11 deg c to 11 deg c = stability
= 11 deg c to 16 deg c = 5 deg c increase
= 11 deg c to 16 deg c = 5 deg c increase but stable from last epoch
= 11 deg c to 16 deg c = 5 deg c increase but stable from last epoch
= 11 deg c to 16 deg c = 5 deg c increase but stable from last epoch
= 11 deg c to 16 deg c = 5 deg c increase but stable from last epoch
Combined brain size evolutions with potential brain neuron evolution ratio with brain size evolutionary time periods with temperature range.
= 320 ml to 380 ml : 1 to 1.2 : 16,000,000 years : 12 deg c decrease
= 380 ml to 618 ml : 1 to 1.6 : 2,200,000 years : 5 deg c increase
= 618 ml to 850 ml : 1 to 1.4 : 900,000 years : stability
= 850 ml to 1100 ml : 1 to 1.3 : 1,300,000 years : 5 deg c increase
= 1100 ml to 1600 ml : 1 to 1.5 : 300,000 years : stability
= 1600 ml to 1200 ml Denisovan decrease : 1 to 0.75 : 50,000 years : stability
= 1200 ml to 380 ml Floriensis decrease : 1 to 0.3 : 156,000 years : stability
= 1600 ml to 1440 ml Neanderthalensis to Sapiens 1.1 to 1 : 55,000 years : stability
Conclusions
The largest decrease in temperature over the longest time periods coincides with an increase in brain size.
The smallest increase in temperature over the second longest time period coincides with the largest increase in brain size.
Stable temperature conditions coincide with brain size increases to a lesser extent than they coincide with brain size reductions.
Therefore temperature changes coincide with changes to the brain size.
Therefore stable temperatures coincide on the whole to a reduction in brain size.
The current climate projections are for an unprecedented 2 to 6 deg c increase in global temperatures over the next 100 years.
Climate change from the data available could vary the human brain size due to environmental adaptation.
Sources:
http://en.wikipedia.org/wiki/Human_evolution
http://en.wikipedia.org/wiki/Australopithecus_afarensis
http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum
http://en.wikipedia.org/wiki/Pliocene_climate
http://en.wikipedia.org/wiki/Plio-Pleistocene
https://www.google.co.uk/#safe=strict&q=earth%20temperature
http://www.livescience.com/40311-pleistocene-epoch.html
http://www.bbc.co.uk/nature/history_of_the_earth/Pleistocene
http://en.wikipedia.org/wiki/Homo_habilis
http://en.wikipedia.org/wiki/Homo_erectus
http://en.wikipedia.org/wiki/Homo_heidelbergensis
http://en.wikipedia.org/wiki/Neanderthal
https://abagond.wordpress.com/2013/07/26/denisovans/
http://en.wikipedia.org/wiki/Homo_floresiensis
http://en.wikipedia.org/wiki/Human
Ian K Whittaker
Websites:
https://sites.google.com/site/architecturearticles
Email: iankwhittaker@gmail.com
20/04/2015
14/10/2020
998 words over 4 pages