Convincing evidence is sorely needed for the assumption made by some scientists that humans are still evolving. Actually, it is often claimed that modern humans have stopped evolving because cultural and technological advancements have annihilated natural selection.
Quite to the contrary, recent studies have shown that selection can be strong in contemporary populations, although detecting a response to selection is particularly difficult.

Searching through the parish records of the Ile aux Coudres, an island which lies in the St.Lawrence River, 80 kilometers North of Quebec City, the capital of the French-Canadian Province of Québec, a team of researchers led by Emmanuel Milot and Denis Réale of the University of Quebec at Montreal have collated the histories of women born on the island between 1799 and 1940.

The researchers found that over this 140-year period, the age at which a woman had her first child — a trait that is highly heritable — fell to 22 years, from 26; because of this change, women on average had four more children during their reproductive lifetime. This finding “supports the idea that humans are still evolving,” the researchers wrote in PNAS.

"Dr. Milot said statistical tests allowed the researchers to distinguish between the effects of natural selection and those of cultural practices affecting the age of marriage.
Studies like those of Île aux Coudres can detect the hand of natural selection only in the data that happen to be recorded in church registries; but many human traits besides those of life history are probably being shaped by natural selection. Many aspects of personality are heritable," Dr. Milot said.

".....In traits that are influenced by many genes, natural selection can act quickly because it does not have to wait for a favorable new mutation to come along. All it needs to do is increase the abundance of some of the genes affecting the trait in question, a process known as a “soft sweep......”

They found a Newfie with only partially webbed feet?

laklak wrote:They found a Newfie with only partially webbed feet?

I might have found your joke funny if it weren't marred by a huge geographical error: Newfi is the nickname for the inhabitants of Newfoundland, which is a place close to Québec but not quite the same.

Does anyone remotely credible actually say that humans are no longer evolving? It's just elementary nonsense.

Federico wrote:The researchers found that over this 140-year period, the age at which a woman had her first child — a trait that is highly heritable — fell to 22 years, from 26; because of this change, women on average had four more children during their reproductive lifetime.

Four years earlier start = four more children?
Did later women also carry on having children to an older age, or have them after age 26 with shorter gaps between than earlier women, or did they manage to have one every year between 22 and 26 (despite breastfeeding) and then carry on as earlier women did?

Very good questions, tolman.
Unfortunately, I don't have the ansersnore any is provided by the link [ http://www.pnas.org/content/early/2011/ ... 8.abstract] PNAS [/url]

An Acadian friend of mine has very narrow eyes, as do the rest of her family. It's said that this is because all the males in her family have been fisherman (mostly crab, which live in deep sea) going back hundreds of years. Narrow eyes have been selected for since it makes it easier to keep the salt out of your eyes.

Federico wrote:

laklak wrote:They found a Newfie with only partially webbed feet?

I might have found your joke funny if it weren't marred by a huge geographical error: Newfi is the nickname for the inhabitants of Newfoundland, which is a place close to Québec but not quite the same.

Newfoundland is the Island, Labrador is the landmass adjacent to Quebec. I don't get the error?

HughMcB wrote:

Federico wrote:

laklak wrote:They found a Newfie with only partially webbed feet?

I might have found your joke funny if it weren't marred by a huge geographical error: Newfi is the nickname for the inhabitants of Newfoundland, which is a place close to Québec but not quite the same.

Newfoundland is the Island, Labrador is the landmass adjacent to Quebec. I don't get the error?

OK, Hugh, the scientific study was done in the Province of Québec where live the "Canayens". The joke of the webbed feet concerns the inhabitants of Newfounndland or Newfies who are not supposed to be very bright. Got it?

Yes, I don't think lak was too concerned with the geographical implications of his statement, merely just replying to the thread title. GOT IT?

Federico wrote:
OK, Hugh, the scientific study was done in the Province of Québec where live the "Canayens". The joke of the webbed feet concerns the inhabitants of Newfounndland or Newfies who are not supposed to be very bright. Got it?

Ahh yes! I have finally got it - although I don't think Lak quite meant it the way you think he meant it. I also don't think he put quite as much thought into it as you did.


But anyway - I am still wondering about my earlier question. Does anyone know of anyone credible that thinks humans have removed themselves from the evolutionary mechanism?

The Borg? They are already perfection! , But you wanted somebody real?

Found it - Not available in your country - but thanks anyway! I will have a look to see some reviews/comments about it,

I hardly understand how age of birth can be related to any genetics aspect. Wouldn't it be more obvious that those women had children at an earlier age due to the church pressure to ensure a competitive growth of the population at the end time of the study?

I've always seen natural selection as passive shift toward an adaptation on which we don't have much control. The decision to produce an average of 15 child per woman isn't what I'd call natural selection since it appear totally artificial (the objective being solely political).

Mathieu has a point.

I consider earlier age at first birth to be far more likely to be a response to cultural change than genetic.

While human evolution still continues, measuring significant change over just a few hundred years seems unlikely.

Lance wrote:Mathieu has a point.

I consider earlier age at first birth to be far more likely to be a response to cultural change than genetic.

While human evolution still continues, measuring significant change over just a few hundred years seems unlikely.

Cultural changes can [and does] affect biological change. Although it may be difficult to separate which one leads and which one follows. The epigentic licencing may, or may not, become fixed in the population over the longer term.

Darwinsbulldog wrote:
Cultural changes can [and does] affect biological change. Although it may be difficult to separate which one leads and which one follows. The epigentic licencing may, or may not, become fixed in the population over the longer term.

Although I have difficulties understanding your concept of "epigentic licencing", it is now a well estblished and scientifically proven fact human evolution continues inarrestably while bringing significant generational changes albeit through a different and more subtle mechanism than gene mutatins which may take indeed thousand of years to manifest itself.
We are now talking of evolution through Epigenetics, which essentially is a somatic change brought about even within a generation by environmentally-induced (mainly) alteration of nuclear protein (histones) regulation of genes' fuctionalty, such as gene-methylation which inactivates the gene.

A discovery made recently at the Université de Montréal by Dr. Stephen Michnick brings further proof for the existence of an additional mechanism for transmission of genetic information which is based on nuclear proteins and which can be influenced by the environment. And I quote:

"We think of genes and proteins interactivity in the same manner as people process sentences," says Dr. Michnick. "Living cells do something similar with genes: proteins read DNA sequence from beginning to end and translate this information in turn into new proteins, which are essentially molecules that build the cells structure and control biochemical processes. But like language, there's much more to it than a simple grammatical problem; there are more abstract processes at the heart of reading genes that we need to understand."
Dr. Michnick, who was recruited to the Université de Montréal from Harvard University, routinely collaborates with top scientists in his quest to know where life began. In a recent study published in the journal PLoS Biology, led by Harvard University's Fred Winston, the University of Toronto's Tim Hughes, Dr. Michnick and the Université de Montréal's Christian Landry helped identify genes that code for proteins that in turn control the reading of genes.

"The study provides insight into the fundamental mechanisms of epigenetic control - gene expression that are controlled by heritable but potentially reversible changes in DNA - which provides a new avenue towards understanding environmental effects on the human genome.
"Epigenetic control is needed to direct the development of an embryonic stem cell, for instance, into a brain as opposed to a kidney cell," Dr. Michnick says. "Control of genes is subject to both inherited and environmental factors, so that genes may be read differently and up to what a person eats or even what their grandmother ate."

An article recently published in The NewScientist entitled "Epigenetic clue to schizophrenia and bipolar disorder " provides new evidence for an epigenetic mode of transmission of Schizophrenia and of Bipolar disorder.

"......TWIN studies have shown that people with schizophrenia and bipolar disorder have changes in gene activity caused by their environment. The finding provides the strongest evidence yet that such gene changes might cause the conditions.
Jonathan Mill at the Institute of Psychiatry, King's College London, and colleagues scanned the genome of 22 pairs of identical twins - chosen because one twin in each pair was diagnosed with schizophrenia or bipolar disorder.

"As expected, the twins had identical DNA. However, they showed significant differences in chemical "epigenetic" markings - changes that do not alter the sequence of DNA but leave chemical marks on genes that dictate how active they are. These changes were on genes that have been linked with bipolar disorder and schizophrenia.
Mill's team scanned for differences in the attachment of chemical methyl groups at 27,000 sites in the genome. Methylation normally switches genes off, and de-methylation turns them on."

"....the most significant differences, with variations of up to 20 per cent in the amount of methylation, were in the promoter "switch" for a gene called ST6GALNAC1, which has been linked with schizophrenia. The twin scans also revealed methylation differences in GPR24, a gene previously linked to bipolar disorder."
•

@Federico

I thought epigenetic licencing was an accepted term?

Johnson, C. L. and A. M. Spence (2011). "Epigenetic Licensing of Germline Gene Expression by Maternal RNA in C. elegans." Science 333(6047): 1311-1314.

RNA can act as a regulator of gene expression with roles in transposon silencing, antiviral defense, and cell fate determination. Here, we show that in Caenorhabditis elegans a maternal transcript of the sex-determining gene fem-1 is required to license expression of a wild-type fem-1 allele in the zygotic germ line. Females homozygous for fem-1 deletions produce heterozygous offspring exhibiting germline feminization, reduced fem-1 activity, and transcript accumulation. Injection of fem-1 RNA incapable of encoding a protein into the maternal germ line rescues this defect in the progeny. The defect in zygotic fem-1 expression is heritable, suggesting that the gene is subject to epigenetic silencing that is prevented by maternal fem-1 transcripts. This mechanism may contribute to protecting the identity and integrity of the germ line.

http://www.sciencemag.org/content/333/6047/1311.full

I suppose at least part of the puzzle is due to the notion of genes being either leaders or followers of evolutionary change. But there is evidence of both modes operating. See Schwander & Leimar (2011):-

Schwander, T. and O. Leimar (2011). "Genes as leaders and followers in evolution." Trends in Ecology & Evolution 26(3): 143-151.

A major question for the study of phenotypic evolution is whether intra- and interspecific diversity originates directly from genetic variation, or instead, as plastic responses to environmental influences initially, followed later by genetic change. In species with discrete alternative phenotypes, evolutionary sequences can be inferred from transitions between environmental and genetic phenotype control, and from losses of phenotypic alternatives. From the available evidence, sequences appear equally probable to start with genetic polymorphism as with polyphenism, with a possible dominance of one or the other for specific trait types. We argue in this review that to evaluate the prevalence of each route, an investigation of both genetic and environmental cues for phenotype determination in several related rather than in isolated species is required.

http://www.sciencedirect.com/science/ar ... 4710003022