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Are humans evolving?

In 2005, Stefasson et al. reported the fascinating discovery of an allele in humans whose presence is associated with increased fertility in Icelandic and European populations. Females with at least one copy of the allele have approximately 3.5%, and males 2.9%, more children on average than non-carriers. The exact mechanism by which the allele affects fertility is unknown.

1. Predict: Consider what you know about evolution. Do you think these populations are likely to be evolving with respect to this allele? Why or why not? Please make sure your response illustrates your understanding of evolution.

2. Test: Describe one way you could test your prediction quantitatively . What data would enable you to conclude that these human populations are evolving? What results would support the contention they are not?

Differential survival and reproduction underpin evolution

The fascinating discovery above should have called to mind the key causes, a.k.a. 'agents', of evolution

  • natural selection
  • sexual selection
  • genetic drift (including bottle necks and founder effects)
  • immigration/emigration
  • mutation

and their consequences. All cause a population to evolve by altering the frequency with which particular phenotypes, their underlying genotypes and most importantly the responsible alleles, occur. This quantitative description of the genetic consequences of these evolutionary mechanisms is encapsulated by the population geneticists definition of evolution:

  • Evolution is a change in the allele frequencies observed in a population over time (i.e. over generations).

Agents of evolution cause allele frequencies to change because they result in differential survival and reproduction. That is, not every individual has an equal chance of surviving, reproducing and contributing surviving offspring to the next generation. (The survival of offspring is key; if you reproduce but your kids don't survive to reproduce then you are evolutionarily inconsequential in terms of your allelic contribution to future generations.) Instead, for reasons that vary with the agent, some phenotypes, and their responsible genotypes, are more likely to survive or to reproduce and thus, to leave behind offspring than other phenotypes (genotypes). As a result, alleles of reproductively successful individuals become more common, and those associated with relatively unsuccessful individuals become less common, in subsequent generations. This change in allele frequencies is, of course, evolution.

Conversely, a population will not evolve if every phenotype (genotype) has an equal probability of surviving and producing surviving offspring. To imagine this, conjure a population in which all of the following conditions are simultaneously met:

  • all phenotypes are equally likely to survive and to reproduce surviving offspring; there is no natural selection.
  • all phenotypes are equally attractive or have equal access to potential mates; there is no sexual selection.
  • no phenotypes leave behind more offspring than others just by chance; the population must be very large as there is no genetic drift.
  • breeding individuals (and their genotypes) are not leaving or entering the population; there is no emigration or immigration.

The genetic consequence of all this equality is that the same allele frequencies are maintained from one generation to the next so the population does not evolve.

Of course, not all organisms reproduce sexually but the point is that a population will not evolve if all genotypes are equally likely to leave behind offspring with their alleles, even if reproduction occurs asexually.

3. Consider these definitions as you reflect your answers to questions 1 and 2 in the "Are Humans Evolving?" scenario above. Have you learned anything that would encourage you to modify your answers? If so, please do. If not, explain why your responses are appropriate.

    Definitions

  • frequency - the number of times an event or observation, for example a particular measurement or condition like blue eyes, is observed in a collection of events or observations like those comprising a sample, population or study. In this statistical sense, a frequency is equivalent to a proportion. For example, the frequency of a particular allele is equal to the number of times that allele is observed in a population over the total number of alleles for that locus in the population. Can be expressed as a fraction, a percentage, a decimal, or a probability.

    Works cited

  • Stefansson, H., Helgason, A., Thorleifsson, G. et al. 2005. A common inversion under selection in Europeans. Nature Genetics . 37:129-137.

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Understanding the hardy-weinberg equation. OpenStax CNX. Oct 22, 2007 Download for free at http://cnx.org/content/col10472/1.1
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