Background trivia
For a true human example of evolution over a few thousand years, evidence the teeth.
The Shape of the Matter Over the course of the last few thousand
years, the human jaw has changed shape dramatically. One of the
broadest trends has been a steady decline in the size of the jaw. From
around 35,000 years ago to about 10,000 years ago human jaws and teeth
decreased in size by about one percent every 2,000 years. For the last
ten thousand years, that pace has increased to roughly one percent
every 1,000 years. In pace with our shrinking teeth and jaw, the
structure of human teeth has changed as well, as thickening enamel and
adaptations in technology have cut back our reliance on strong,
well-ordered teeth.
Cooking has had one of the largest effects on the development of human
dentition. In the distant past, when much of our diet was raw fruits
and vegetables, we needed strong and straight teeth. These helped us
push our way through the tough, large particles that made up our diet.
Cooking has reduced our need for this ability dramatically. At its
simplest, the primary goal in cooking food is to break down tough
fibers in meats and vegetables, rendering our meals proportionally
easier to digest. As a result, the evolutionary pressure to keep our
teeth well-ordered has dropped away.
Another example of subtle human changes over time is height.
“Over the past century adult height has changed substantially and
unevenly in the world’s countries, according to research published in
the journal eLife.
Authors found that people from central and southern Europe, as well as
East Asia, grew taller in the last 100 years. Meanwhile there was
little gain in height for people from sub-Saharan African and South
Asian nations. A few countries experienced decreases in their average
adult height after years of gain.
Researchers found that Dutch men, at 182.5 centimeters (about 6 feet),
and Latvian women, at 170 centimeters (5 feet 7 inches), are the
tallest in the world .
Men from Timor-Leste, at 160 centimeters (5 feet 3 inches), and
Guatemalan women, at 149 centimeters (4 feet 11 inches), are
considered the shortest.
There would most certainly be changes due to the Martian environment. I would suspect that over 3,000 years, the differences would be small but significant.
And I suspect the changes would have to be more about gene expression and epigenetics than genetic mutation. Existing but unused, unexpressed genes in the human genome would be expressed in a different manner, due to environmental pressures.
While the genome is fixed, the epigenome is much more dynamic.
Epigenetic modifications would allow individuals to quickly explore an
adaptation to a change in the environment, without “engraving” this
adaptive change into the genome. The challenges of epigenetics concern
not only medicine and public health (see Epigenetics, the Genome and
its Environment) but also evolution (see Theory of evolution:
misunderstandings and resistance). Indeed, it casts suspicion on the
environment that could modulate the activity of some of our genes to
modify our traits, or even induce certain diseases potentially
transmissible to offspring. Clearly, the Dutch famine of the winter of
1944-1945 shows that permanent changes have occurred in the genetic
heritage of the women who were pregnant at this time and then passed
on from generation to generation. This would mean that the trauma also
affects the germ cells (sperm and eggs), the only biological link
between generations.
I would not expect major physiological changes over this period, but I would posit instead a myriad of subtle changes that, because they are dependent on existing genes in the human genome, and in the unknown Martian environment (it depends a lot on how much Humans adapt that environment) the changes are are unpredictable.
The issue is also compounded by 'selective migration'. I would expect that those who migrate to Mars would be a unique sub-set of the human genomic code. The entire colonization of Mars would be beset by complications and hazards, with a unique selective process. Humans that can survive the trip and the colonization experience, survive. Those that don't, either die or return to Earth. The genetic makeup of Martians over 3,000 years would be very dependent on the genetic makeup of the first thousand or so colonizers, who would have been subject to extreme 'self-selection' criteria.
