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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.


  • 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

how environment affect demand and supply of commodity ?
Amos Reply
Wht at the criteria for market ?
what is difference between monitory policy and fiscal policy?
Malik Reply
monetary policy is a policy thrust by National Govt(CBN) to influence government spending, purchase &taxes
necessity of economics
Pamela Reply
I will say want,choice,opportunity cost,scarcity,scale of preference
what is monopoly market.How price output are determined under monopoly market
b) Monopoly market is an impecfect market where s single firm having the innovation to produce a particular commodity.Prices are determined through output since there are no other competitive.
Monopoly market:firm has market power & does not respond to market price
Explain the process of price determination under perfect competition market with suitable diagram
bisham Reply
Price determination under perfect competition via this process :firms have no market power to influence price rather firms respond to market price.
price is different from demand- demand is amount of commodity
Effah Reply
demand is amount /quantity of commodity a potential buyer is willing to buy at a given price at market
demand is a desire of customer on commodity with the ability to pay it and willing to buy it at given price of commodity
demand is price of what
Faith Reply
show that shortrun average cost
Baby Reply
what is economics
Mbah Reply
what is money
what is money
Difine macro economics
money is a medium of exchange between goods and services,maybe inform of currency.
Economics is study of how human beings strive to satisfy numerous wants using limited available resources.
how do you find the maximum number of workers the firms should employ order to produce where there are increasing returns
what are implications of computing national income?.
what is the formulae for calculating national income
it calculated by value added method
classify the production units like agriculture, banking, transport etc
money is anything that is generally acceptetable for human
Estimate the net value added(NVA) at fixed cost by each industrial structure
definition of unemployment
Adam Reply
what are the causes of unemployment?
Mbubi Reply
The main causes of unemployment are listed below. 1. Frictional unemployment 2. Cyclical unemployment 3. Structural unemployment
We can also categorize the causes on a broader sense as: 1. Political and 2. Social cause As unemployeement root causes are embaded in this two.
would opportunity cost exist if there was no scarcity?
yes just because the opportunity cost arose when there is Alternative to choose among the alternatives.
I am thinking that, if our resources were unlimited, then there wouldn't be any need to forgo some wants. Hence the inexistence if opportunity cost
politics has done what?
consider time assani
I'm Emmanuel,...I taught the main cause is the change in gov't.
...Lack of capital to set up a firm respectively
I would like to bring in Educational levels can also be the cause the cause of the problem respectively
lack of skills among the new generation is the serious issue.
Where I come from , I don't see why education or personal aspects seem to do with unimployment, technically the motivation and eigerness in all works of live is there , dispite the cultural influence and physical bearriors;the thing we lacking is Government Support and open market ethics.
sorry about that-(repation). We have a over powering ethical political system that's displacing the marketing asspects of economy and causing large scale unemployment right across the board...
can someone Explain Expansionary Monetary Policy and Contractionary Monetary Policy Using one of the instrument of Monetary Policy? Please am kinda lost here?. ta
Emmanuel Reply
using a graph show the case of substitute and compliment goods
Ade Reply
can anyone give me a simple explanation to Five Sector Macroeconomics?
Can someone please define what economics is
jason Reply
economics simply is a social science subject that study human behavior.
economics is a social science which studies human behaviour as a relationship between ends and scarce means that has alternative uses
Can someone please tell me how to calculate GDP
emmanual kapal to calculate GDP (Gross Domestic Product) has three method in calculating it (1)income approach (2) expenditure approach (3) value added method
thanks Alae
u are welcome
in basic terms economics is revered to as battery system, it date back to when Men sees the need to exchange sapless goods and produce to gain , either wealth , basic necessities or to establish trading ties for personal benefit or social asspects in terms of coexistence and continuity, future .
what is the law of demand
Berlinda Reply
keep other thing constant, when the price increases demand decrease when the price decreases demand increases of the commodity.
all things being equal,quantity demanded decrease as price increase and increase as price decrease
there's practial joke to it ..." the higher the demand ; scarcity, increase in production and drop in quality"... quite the controversy - for example China vs Europe, United States and we are all boxed up in between somewhere...
Other thing remain constant the low price of commodity the high quantity of commodity and vice versa is true
Explain Effective demand
Anita Reply
What is effective demand
like Modi is in demand...best example of effective demand
Don't get you
Anita you mean you don't get me or who?
level of demand that represents a real intention to purchase by people with the means to pay
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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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