Geological Time, Evolution and Human Effects

30 December  2020

Thomas Jefferson is known mostly for being the primary author of our Constitution, but he also was a prolific inventor and in that, he recognized the effects of evolution. In one example, his bed at Monticello is situation between two walls, one at the head and the other at the foot, enabling it to be raised or lowered, depending on whether the space was to be used for sleeping or sitting. In this case, the distance from head to toe was notably short, where a modern human would not be at all comfortable. The explanation of this was that humans were much shorter in colonial times than we are now, in other words, we have changed, evolved, with time, due to environmental effects.

While the presence of Mastodons in Mineola is not necessarily documented, the association of Osage Orange (Bois D’arc) trees and Mastodons has been suggested by Barlow (2000) and their linage does date back to these earlier times. Further, there are many fossilized remains of Woolly Mammoths and other ancient creatures throughout Texas, e.g.

With the Universe being 13.9 billion years old, and recognizing the significant events described elsewhere on these pages, the scaling and descripition  of the various stages in the Earth’s history is difficult since it involves very large time spans, compared to the very short history of the Earth, which is mostly within 4.5 billion years.  Many changes have obviously occurred in order to come from the Big Bang to the big blue planet that we are today. (Spearing. 1991).

To work with these time frames and events, geologists have defined several eras as follows:  Cenozoic (now to 66 million years); Mesozoic (previous to 345 My); Paleozoic (to 570 My) and Precambriam (to 4.5 billion years}. Ages of the various rocks are determined with carbon dating techniques where the analyzed state is the final, stable state existing at the time of the dating. Human effects on the Earth have been very recent and are identified as the Holocene age of up to 11,700 years preceded by the Upper and Middle Pleistocene, Calabrian and Gelasian up to approximately 2.6 Million years. In these periods, geologists have identified time periods when significant land use occurred and expanded (roughly 5,000 years). Other much more recent time spans are when large dams were constructed and when water began to be largely used as well as fertilizer. These are all in the Anthropocene epoch at the top of the Holocene. (Monastersky, 2015).

Evolution has played a significant role in the development of plant and animal life and Barlow (2000) has reviewed the mutual adaptability of these two kingdoms. A plant based example of the evolutionary change with time is in the history of the osage orange, or Bois D’arc tree, found in Northeast Texas.  The fruit is baseball sized and is extremely hard. It previously provided food for the mastodons. In this case the strong tooth and bone structure of the jaw enabled this creature to pull the fruit off of the tree and crush it before swallowing.


These Osage Orange trees  (Maclura pomifera) found in Mineola, Texas are   members of the genus Maclura and  of the many relatives from past geologic eras, only fossils remain


Evolution has caused the demise of the animals previously eating these fruits yet the osage orange is still around. A car parked under one of the trees growing the osage orange will risk suffering a paint chip or dent when the hard fruit falls off of the limb. They also can be thrown like a baseball by young boys.

Leafcutter ants are cited by Barlow (1997) as an example of evolutionary achievement for their well tended fungal garden. The image below shows a leaf from a nearby tree being moved by the leafcutter ant to its nest. 

The dark matter shows foraging trails used by the ant in its harvesting and growth activities.

Leaf cutter ant with leaf on foraging trail – A

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