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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

find the 15th term of the geometric sequince whose first is 18 and last term of 387
Jerwin Reply
I know this work
salma
The given of f(x=x-2. then what is the value of this f(3) 5f(x+1)
virgelyn Reply
hmm well what is the answer
Abhi
how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
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ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
hmm
Abhi
is it a question of log
Abhi
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I rally confuse this number And equations too I need exactly help
salma
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salma
Commplementary angles
Idrissa Reply
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Sherica
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Sherica
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Tamia
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Uday
hi
salma
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
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Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
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rolling four fair dice and getting an even number an all four dice
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Kristine 2*2*2=8
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Differences Between Laspeyres and Paasche Indices
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No. 7x -4y is simplified from 4x + (3y + 3x) -7y
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how do you translate this in Algebraic Expressions
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Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
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. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
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what's the easiest and fastest way to the synthesize AgNP?
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China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
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Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
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what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
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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