Human Evolution: Insights into Our Past and Future
Human Evolution: A Journey Through Time
How long have Homo sapiens been around?
Approximately 200,000 years.
How long does evolution take to change species?
Evolutionary changes typically require a significant amount of time.
When did the mutation that permits earthworms to survive happen?
More than 170 years ago.
How big is the difference between these earthworms and “normal” earthworms?
The difference is comparable to that between a human and a mouse, representing different species.
What drove the evolution of the difference in the earthworms?
Natural selection is the driving force behind this evolution.
Are humans exposed to the environmental changes that seem to drive evolution in other species? If not, what has stopped us from evolving?
Humans often defend themselves against environmental changes, reducing the need to adapt.
What is the difference between a 33,000-year-old skeleton and one of today?
They are essentially the same.
What is one obvious way that humans have evolved in the last 60,000 years?
The color of our skin has changed; in the past, we were all dark-skinned.
Where do we need to look to find out if people are still evolving?
We need to look at populations in environments that are different from our normal society.
Why are these environments the place to look?
Because they present unique challenges, such as high altitudes.
How long have people lived there?
Thousands of years, such as when Sherpas migrated to the mountains.
How would our bodies adapt to cope with the altitude?
By generating more red blood cells.
How have the Sherpas evolved to live at that altitude?
Their blood flow is different, with faster circulation and more capillaries.
Is this evolution by natural selection?
Yes.
By examining our genome, how many examples of mutations that have undergone natural selection recently have been found?
Approximately 250.
Give some examples of mutations driven by environmental change.
Mutations that allow adaptation to high altitudes, like in Sherpas.
When did the mutation that allowed most Europeans to digest milk happen?
Around 10,000 years ago.
How is it linked to farming?
Farming caused the change.
How is this change different from the others seen so far?
It is driven by changes made by man on his environment. What has caused the slowdown in natural selection? The deaths of babies.
What percentage of babies live to be 21 today?
99 percent.
In Darwin’s time, what percentage of babies lived to be 21?
1 in 2.
What two things have caused the difference?
Babies die because of their natural selection.
So what do we need to control to keep escaping natural selection?
Control diseases.
What is the popular theory as to what has caused the evolution in the chicken virus?
Vaccinating the chickens allowed the virus more time in the cells to mutate.
Why won’t we be able to win the war against infectious diseases?
They are evolving while we are making medications to cure them.
Now that most people survive long enough to pass on their genes, what might now be driving evolution?
The number of kids that parents are having.
What will the future inhabitants of Framingham look like according to the research of Stephen Stearns?
Reduced height and a bit more weight.
What does professor Stearns say about the patterns of this type of variation?
It is moving all the time until something stops it to move in one direction.
What does he say can cause a change in this pattern?
Changing the environment.
Will the people of Framingham get ever fatter and shorter?
What does he believe will cause the biggest change in our environment and therefore have the biggest effect on our future evolution?
The way that we live.
How do they know what traits the different embryos have?
Separating cells from the embryo to study them individually.
What are the things that people can choose and which are the ones that they can’t choose?
They can choose the sex of the baby, but they are not able to choose characteristics such as hair color, or if they are going to be tall or small.
What determines what can be selected for or not?
Whether it is ethical or not.
Is it a good idea to be able to choose these traits?
They don’t know.
What are the two things that affect the way we evolve?
Are we the most evolved organism on the planet?