Once researchers had figured out when
cannabis first diverged from a common
ancestor, the question of where still remained.
Paleobotanists then turned to microfossils,
such as fossilised pollen, to fill in the records.
They found that pollen from the closely
related cannabis and hop plants are almost
indistinguishable.
To overcome this problem, scientists realised
that because cannabis typically grows in open
grasslands, and hops grow in forests, the
pollen could be classified by identifying other
plants that commonly occur alongside it.
Researchers used plants that are typically seen
in open grasslands to identify the fossilised
pollen as cannabis.
How Scientists Dated and Located Fossilised
Cannabis Pollen
Fossilised pollen is usually used to date the
layer in which it is found, which tells a lot
about the environment at the time. However,
in this case, the pollen was the unknown.
Researchers aged it with radiocarbon dating.
Radiocarbon dating measures the amount of
radiocarbon (C14) left in a fossilised animal
or plant.
C14 degrades at a known rate, and so by
testing the amount of C14 left in a fossil, its
age can be accurately calculated.
By using this analysis, the oldest fossilised
cannabis pollen was located in the Ningxia
Province, China.
Researchers dated the pollen at 19.6 million
years old.
But with cannabis diverging 27.8 million
years ago, this date wasn’t close enough.
Cannabis stems from a single location on the Tibetan Plateau
Further research of the region and tracking of
a plant called Artemisia, which has a close
alliance and parallel evolutionary pattern to
cannabis, pinpointed the north-eastern
Tibetan Plateau as the cannabis centre of
origin.
At the time, the Tibetan Plateau created an
environment that supports the theory that
cannabinoids developed to protect the plant
from UV rays and herbivores.
These are both issues in the high altitude,
open grassland Tibetan Plateau.
Fossil pollen records tell us that cannabis
dispersed into Europe 6 million years ago.
Then later East into China 1.2 million years
ago. By mapping the distribution of pollen
over time, scientists were able to see that
European cannabis went through repeated
genetic bottlenecks.
Following the warm and wet Holocene
period, forests replaced open grasslands.
Cannabis retreated to the small pockets of
open space that it could inhabit.
In these small and isolated areas, the
population of cannabis shrank.
These separated cannabis populations then
evolved differently, eventually creating the
separate and distinct landrace strains of the
European-evolved sativa and the Asian-
evolved Indica.
By tracing cannabis evolution back to a single
location on the Tibetan Plateau millions of
years ago, we have uncovered the site of the
original cannabis landrace strain.
Over thousands of years, the original cannabis
strain moved across continents, becoming
isolated in certain areas.
The original landrace strain had to then
develop to new conditions, eventually leading
to a variety of landrace strains. Each
developed
unique
Geno-phenotypical
characteristics reflective of adaptations
provoked by their local environment. And
these ancient strains have become the
mythologised landrace strains that we idolize
today.
https://www.rxleaf.com/fossilized-cannabis-original-
land-race-evolution/