GEOLOGY 3Field Assignment

By

April Chavarria

HOMOSAPIANS

The current theory of evolution is that over the

generations, in our population, we get random genetic

changes (mutations) in our DNA (genome). Most of

these changes are harmless and they might have a

chance to be fixed within a population at a low frequency.

For centuries, writers have attempted to predict the

future of the human race. Some have argued that we are

destined to evolve into super-beings, others that we are

turning into dim-witted goblins incapable of anything

more demanding than watching TV.

But according to a leading geneticist, both visions are

wrong because human evolution has ground to a halt.

Professor Steve Jones, of University College London,

says the forces driving evolution - such as natural

selection and genetic mutation - no longer play an

important role in our lives. (www.dailymail.co.uk)

The people living one million years from now, should

Man survive, will resemble modern-day humans.

In a harsh environment where people are competing to

survive, natural selection is a potent force. So in Ice Age

Britain, a mutation which gave a baby more resilience

against the cold or famine also gave it a strong

competitive edge, making it more likely to survive and

pass its genes on to others. But in a modern world of

central heating and plenty of food, the same mutation is

far less likely to give a child any advantage

There are some factors that can factor into our evolution in years to come. If we look at 100 years from now, it is an incredibly small period of time for evolution to work so any trends we may think we see may not turn out to become fixed in the population. But here are a few that might:

Poor eyesight - having less than perfect vision no longer means that you are at a disadvantage because it can be corrected. So more people will survive with defective vision and pass on this to the next generation.

Low birth weight / premature birth - as children who are born at low birth weight or prematurely now more often survive due to incubators and other medical interventions, any genetic tendency towards low birth weight or premature birth may become fixed in the population.

The appendix is a largely vestigial organ - it has minimal functionality (it may have some small function in combating infection). The reason we still have an appendix is that being born either with or without one makes no difference to our survival rate - therefore there is no evolutionary pressure to either retain it or discard it. (www.yahooanswers.com)

How we Evolve: How are we evolving?

FOOD HORMONES AND EVOLUTION

Early puberty in girls has been found to be associated with a

higher risk for breast cancer. Height, weight, diet, exercise, and

family history have all been found to influence age of puberty .

Steroid hormones in food were suspected to cause early

puberty in girls in some reports. However, exposure to higher

than natural levels of steroid hormones through hormone-

treated meat or poultry has never been documented. Large

epidemiological studies have not been done to see whether or

not early puberty in developing girls is associated with having

eaten growth hormone-treated foods.

A concern about an increase in cases of girls reaching puberty

or menarche early (at age eight or younger) in Puerto Rico, led

to an investigation in the early 1980s by the Centers for

Disease Control (CDC). Samples of meat and chicken from

Puerto Rico were tested for steroid hormone residues. One

laboratory found a chicken sample from a local market to have

higher than normal level of estrogen. Also, residues of zeranol

were reported in the blood of some of the girls who had

reached puberty early. However, these results could not be

verified by other laboratories. Following CDC's investigation,

USDA tested 150 to 200 beef, poultry and milk samples from

Puerto Rico in 1985, and found no residues of DES, zeranol or

estrogen in these samples.

In another study in Italy, steroid hormone residues in beef and

poultry in school meals were suspected as the cause of breast

enlargement in very young girls and boys. However, the

suspect beef and poultry samples were not available to test for

the presence of hormones. Without proof that exposure to

higher levels of steroid hormones occurred through food, it is

not possible to conclude whether or not eating hormone-

treated meat or poultry caused the breast enlargement in these

cases. (www.cornell.edu)

In these pictures, my daughter is

only 16 years old.

OBESITY AND EVOLUTION

Obesity - being obese no longer

means being unable to escape a

predator or defeat a rival in battle

as in earlier stages of evolution.

Any tendency towards obesity is

likely to become fixed in the

population.

Obesity Statistics