The intelligence of the African Forest

About 3-5 million years ago is the last time carbon dioxide levels are as high as today.  Sea levels hover at 10-30 meters above current levels and the global average temperatures reach 4 degrees higher than the present.  Greenland is ice-free and temperate. Life fills the planet.  Mammals adapt to specific climates and habitats across the globe.  (more)

Back to 100 million years ago

Forward to 1 million years ago

Mammals evolve for every habitat

Base map adapted from Ron Blakey DeepTimeMaps.com

Movement of continents

Measures 

Forward to 1M years ago

Back to 100 million years ago

Source: CO2

Source: Temp

Source: Sea level 

Sea Level

in hundreds of meters from datum in 1900

Shaded area shows 

uncertainty,

Dotted line is model

Sea level high ~ 30 meters

Temperature high ~ 19° C

Tens of Millions of years

10 million years ago the climate overall is warmer and wetter without ice age cold although it still fluctuates with the cycles of earth’s orbit. In the warm periods northern latitudes warm by as much as 6°C and oceans hold permanent el nino-like heat.

In Africa complex social behavior and intelligence emerges in diverse species, including parrots, elephants and the many lineages of primates, which travel the forest as connoisseurs of its riches.  In this intellectually competitive world, the apes that would become humans and their cousins, chimpanzees, differentiate from the gorillas.  They are the first primates to hunt, and they develop hand gestures to communicate silently.  In the forest they climb easily through the 3-dimensional space of the tree canopy under a dappled dome of leaves.

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On each continent, flora and fauna evolve in isolation since the breakup of Pangea about 150 million years ago.  Australia, South America and Madagascar remain separated far longer than other continents, developing entire families of animals unique to their locale.  This isolation also left plants and animals vulnerable when foreign species finally did enter, as when the isthmus of Panama formed 3 million years ago, allowing North American animals to walk south.

Over tens of millions of years, major evolutionary changes in large animals becomes apparent.  Although evolution can be observed at much shorter timescales, even days or weeks for microbes, and modifications such as the size of the beak of the finch observed by Darwin can happen in a few years.  But the evolutionary tree of familiar animals plays out over long time-spans that encompass myriad genetic mutations that may or may not survive the selection pressures of competitive life in a changing world. 

References

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Image: Composite of Adobe Stock images.  Parrots from photo by World Wildlife Fund and National Geographic

Map: MapLarge. (2018). "GlobalFloodMap.org,."   Retrieved 23 September 2018, 2018, from GlobalFloodMap.org,.

CO2: Pearson, P. N. and M. R. Palmer (2000). "Atmospheric carbon dioxide concentrations over the past 60 million years." Nature 406: 695-699. https://doi.org/10.1038/35021000

Stap, L. B., B. Boera, M. Ziegler, R. Bintan, L. J. Louren and R. S. W. van de Wala (2016). "CO2 over the past 5 million years: Continuous simulation and new δ11B-based proxy data." Earth and Planetary Science Letters 439: 1-10.https://doi.org/10.1016/j.epsl.2016.01.022

Temperature and Sea Level: James Hansen, M. S., Gary Russell, Pushker Kharecha (2013). "Climate sensitivity, sea level and atmospheric carbon dioxide." Philosophical Transactions of the Royal Society A: Mathematical, Physical, and Engineering Sciences 371(20120294).http://dx.doi.org/10.1098/rsta.2012.0294

Miller, K. G., M. A. Kominz, et al. (2005). "The Phanerozoic Record of Global Sea-Level Change." Science 310(5752): 1293-1298. doi.org/10.1126/science.1116412

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