Eske Willerslev and his colleagues,
at the University of Copenhagen, in Denmark, began studying DNA from bacteria
on teeth that caused plague during the Bronze Age and Iron Age. This time was
marked between 4,800 and 3,000 years ago. Willerslev concluded the early plague
germ,
Yersinia pestis, was spread
from person to person among the herders migrating across Europe and Asia during
the Bronze Age. Coughing could have spread the plague, and if the germ caused a
lung infection, the illness was considered
pneumonic
plague. If the blood of an individual became infected, it was considered
septicemic plague.
Willerslev
and his team identified Y. pestis DNA on teeth from Bronze and Iron Age
individuals. The DNA pieces showed up in seven of the 101 people. Two people
with the strain were from Russia roughly 4,800 years ago. Another was from
North Central Europe, 4,500 years ago. The third infected person examined was in
West Asia from almost 4,200 years ago. Several more teeth collected were from
Siberia and Poland and were 3,700 to 4,000 years old. The last sample was from
an individual who lived in Armenia 3,000 years ago.
From the
evidence Willerslev and his team gathered, it is clear the germ spread over a
wide area and for a large amount of time. Further investigation was concluded
of the entire genome in the Bronze Age DNA. The analysis showed the earlier
germ lacked the gene, which was present in the Iron Age individual. This gene
allowed bacterium to survive in a flea’s gut. The plague germ would have been able
to spread via flea bites at some point during 3,700 and 3,000 years ago.
The
biologists have compared plague DNA in one of the oldest Bronze Age individuals
and the most recent Bronze Age individual and concluded both lacked a form of
one plague gene that keeps an infected persons immune system from attacking the
disease. This suggests that the earlier forms of the germ would have been
vulnerable to attacks by the immune system.
One reason
I found this article to be interesting was due to the time periods Willerslev
and his team worked with. They collected and screened 89 billion pieces of DNA
from teeth of individuals from the Bronze and Iron Age. That was almost 5,000
years ago! It is fascinating to know a scientist can pull ancient DNA from teeth of individuals
that lived thousands of years ago. Another captivating point in the article
mentioned this disease took over even when there really was no urbanization.
But certainly this plague evolved and survived longer than expected.
Aging does not carry over to the next generation of progeny. There is no inheritance of the age of your parents and the germ-line cells are responsible. Once thought to be ageless or immortal but found to be untrue, the germ-line cells now are thought to possess a function that acts as a reset on their age. In a new study, scientists report that both mouse and human germ-line cells reset their age early in embryo development. The biological clock of a mouse embryo being studied was constant and unchanging but after 6 to 8 days, the age had taken a dip. The understanding of this process and the ability to control it could lead to further advances on battling age-related diseases like arthritis or Parkinson's. It is still unknown what the mechanism behind the age changes in these early developmental cells and further research will be necessary to uncover it.
