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What were the authors trying to test, and what predictions did they make?

The authors were trying to test the effects of road networks on genetic diversity and connectivity of populations. They predicted that roads and highways would reduce connectivity among populations of flora and fauna. The large number of roads is expected to hinder gene flow, and facilitate genetic drift. Under these conditions, species isolated by roads would likely lose genetic diversity. Population extinction rates are also expected to increase due to inbreeding and reduced evolutionary potential.

What, exactly, did the authors do?

    The authors studied 27 populations of desert bighorn sheep. Over three years genetic samples of the sheep were collected across the study area, primarily by means of fecal pellets. Fourteen different microsatellite loci were genotyped. Female dispersal rates were also studied by examining mitochondrial DNA. Female bighorn sheep are less likely to disperse, so maternally transmitted mitochondrial DNA was used to study dispersal rates.

What did the authors find (i.e, what were their data)?

    The authors found that “the amount of gene flow among populations was strongly and negatively correlated with barriers at interpopulation distances of less than 15 km.” Furthermore, gene flow was weakly and negatively correlated with barriers at distances between 15 and 30 km. The two variables were not correlated after distances of 30km. There was a low correlation of mitochondrial DNA diversity with both barriers and distance. Genetic simulations were also used, and showed that the genetic distance between populations could be influenced by barriers constructed only 40 years ago.

How did the authors interpret their findings?

The authors concluded that genetic diversity for bighorn sheep was negatively correlated with barriers, such as roads and highways. From the results, the authors estimate that genetic diversity had decreased by 15%, for populations completely isolated by barriers. The low correlation of mitochondrial DNA diversity with both barriers and distance may be due to low dispersal rates of the female sheep. Finally, the authors highlight the significance of their finding in a world with a rapidly increasing number of man made barriers “These results suggest that anthropogenic barriers constitute a severe threat to the persistence of naturally fragmented populations.” Underpasses and overpasses have been used successfully to aid in gene flow and help mitigate this issue.

What were the authors trying to test, and what predictions did they make?

Elk were introduced to Afognak Island, Alaska in 1929. Only 8 elk were introduced, but the population peaked at 1,400 in 2009. The authors studied specific loci in this unique population to examine founder effect and bottleneck effect. The purpose of the experiment was to determine the effects of translocation and demography on genetic variation. The isolated population was expected to vary significantly from their parent population due to the population experiencing a genetic bottleneck and founder effect. Therefore the population would suffer a significant loss in allelic diversity.

What, exactly, did the authors do?

The authors studied microsatellite loci in the Afognak population and compared them to the parent population. Microsatellites were used because they have a high degree of polymorphism. Tissue samples of elk from Afognak island and Olympic Peninsula were conducted. The Olympic Peninsula is where the elk that were introduced to Afognak island originated from. DNA extraction, amplification and genotyping took place, fifteen specific microsatellites were chosen to represent the elk genome.

What did the authors find (i.e, what were their data)?

The authors found that the two populations of Elk differed in both allele and genotype frequencies. Specifically 10 of 15 allele frequencies differed, and 11 of 15 genotype frequencies differed.  One specific loci exhibited excess heterozygosity in Afognak. Another loci exhibited a deficit in heterozygosity in the Olympic population. The inbreeding coefficient for the Afognak population was 0.019, and -0.006 for the founder population. Surprisingly, a genetic bottleneck in the Afognak population was not found.“Despite the demographic bottleneck, no evidence of a genetic bottleneck in the Afognak population was detected using a test for heterozygosity excess or mode shift of allele frequencies.”

How did the authors interpret their findings?

    The authors concluded that the combined founder and bottleneck effect resulted in a significant reduction in allelic diversity and heterozygosity. They were unable to reject the null hypothesis of no bottleneck and no inbreeding. One possible source of error is that the Olympic population, which yielded the Afognak founders, was not genetically identical 70 years later. This study demonstrated bottleneck detection, which  can be a helpful tool for endangered species management.

What were the authors trying to test, and what predictions did they make?

    The authors of the article were trying to determine consanguinity rates and the rate of inbreeding in the United Arab Emirates. The authors predicted that although the number of consanguineous marriages are generally declining, due to culture variances Middle Eastern Arabs will have a higher consanguinity rate. The purpose of the study is to find the inbreeding coefficient in the UAE.

What, exactly, did the authors do?

    The authors sampled 2,033 married UAE women, aged 15 or older. The women were interviewed face to face by physicians and qualified nurses. The genetic relationship between the two spouses and whether their parents were consanguineous was recorded.

What did the authors find (i.e, what were their data)?

The authors determined that the rate of consanguinity in the current generation was 50.5%. The coefficient of inbreeding was 0.0222. Marriages between first cousins was the most common type of consanguineous marriage. The authors also believed that their sample size was large enough to apply to the entire population: “It is believed that the sample size is adequate to achieve a high degree of precision in estimating the true incidence rate in the general population.”

How did the authors interpret their findings?

    The authors determined that the coefficient of inbreeding increased between the parent and current generation. The coefficient of inbreeding was 0.0243 versus 0.0158, and the consanguinity rate was 50.5% versus 39%. Over one quarter of all marriages were first cousin marriages. The authors state that this is similar to other Arab countries, and reflects cultural practices. The inbreeding coefficient is increasing in UAE, which is contrast to many populations such as Japan.

Group Members: Maria, Victoria, Trevor

Analyze the correlation between hours slept per week and GPA.

Make a scatterplot with hours slept per week on the x axis and GPA on the y axis to visualize the relationship.

Note any outliers

Another example of modern convergent evolution is human adaptation to tropical rainforests. Tropical rainforests are harsh environments for humans. They are marked with high pathogen activity, high temperatures and abundant rainfall, as well as ferocious animals. This type of unforgiving environment likely resulted in human adaptations in response to selective pressures. Researchers studied 660,918 SNP’s looking for outliers in populations living in a tropical rainforest and genetically related populations living outside of the tropical rainforest in Africa, North America and South America. “The most significant positive selection signals were found in genes related to lipid metabolism, the immune system, body development, and RNA Polymerase III transcription initiation. The results are discussed in the light of putative tropical forest selective pressures, namely food scarcity, high prevalence of pathogens, difficulty to move, and inefficient thermoregulation (Carlos Amorim et al., 2015).” Researchers identified seven clusters in five separate chromosomes that show positive selection for potential rain forest adaptations. Two of the clusters only showed evidence of positive selection in North America and South America. Two other clusters only showed evidence of positive selection in Africa. The other three clusters were found in both continents. This is clear evidence of convergent evolution in modern human history.

There is no scientifically accepted research that shows that humans have stopped evolving. Evolution is certainly still occurring and will continue to occur in humans. Humans exhibit differences in reproductive success, which directly leads to evolution. Humans still face challenges to survival as well, and exhibit variation in heritable traits, all characteristics of evolution. Some of the confusion on this topic likely arises because modern humans have not existed for an extensive period of time, evolutionarily speaking. Many of humanities most esteemed innovations have happened in the past decade or century, merely a few generations at most. However, no innovation will change the fact that humans exhibit varying reproductive success and challenges to survival, the components of evolution.

Another example of modern convergent evolution is human adaptation to tropical rainforests. Tropical rainforests are harsh environments for humans. They are marked with high pathogen activity, high temperatures and abundant rainfall, as well as ferocious animals. This type of unforgiving environment likely resulted in human adaptations in response to selective pressures. Researchers studied 660,918 SNP’s looking for outliers in populations living in a tropical rainforest and genetically related populations living outside of the tropical rainforest in Africa, North America and South America. “The most significant positive selection signals were found in genes related to lipid metabolism, the immune system, body development, and RNA Polymerase III transcription initiation. The results are discussed in the light of putative tropical forest selective pressures, namely food scarcity, high prevalence of pathogens, difficulty to move, and inefficient thermoregulation (Carlos Amorim et al., 2015).” Researchers identified seven clusters in five separate chromosomes that show positive selection for potential rain forest adaptations. Two of the clusters only showed evidence of positive selection in North America and South America. Two other clusters only showed evidence of positive selection in Africa. The other three clusters were found in both continents. This is clear evidence of convergent evolution in modern human history.

There are two main hypotheses regarding the lactose persistence mutation. Firstly, the “culture-historical hypothesis” states that alleles for lactose persistence were low until humans domesticated dairy animals in the early Neolithic and then rose sharply due to the selective advantage it conferred and natural selection. The “reverse cause hypothesis” states that dairy animals were utilized in populations with preadaptive high lactose persistence. Researchers have discovered that lactase persistence likely arouse through convergent adaptation. Scientists studied 470 Tanzanians, Kenyans and Sudanese in a genotype-phenotype association study which focused on three SNPs associated with lactase persistence “These SNPs originated on different haplotype backgrounds from the European SNP and from each other...These data provide a marked example of convergent evolution due to strong selective pressure resulting from shared cultural traits—animal domestication and adult milk consumption. (Sarah Tishkoff et al., 2007)” This case of convergent evolution with African and European populations is strong evidence that human populations are evolving. Mutations likely arose independently in these two populations that allowed for lactase persistence. Since the mutations conferred a selective advantage, these alleles were favored by natural selection and increased in frequency.

Another prominent example of recent evolution resides within the ability to drink and digest milk. Most human adults are incapable of digesting lactose and therefore milk. Babies are capable of drinking milk due to a gene that codes for lactase, which breaks down lactose. In people who are lactose intolerant, the gene essentially switches off after weaning. However, a mutation known as lactase persistence arose in recent human history that allowed lactase to be produced into adulthood. This trait likely provided a selective advantage to individuals with access to domesticated dairy animals, who consumed the unfermented milk. “Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for lactose persistence, although it has not been possible to say whether early Neolithic European populations were lactase persistent… (J. Burger et al., 2006)”

Another prominent example of recent evolution resides within the ability to drink and digest milk. Most human adults are incapable of digesting lactose and therefore milk. Babies are capable of drinking milk due to a gene that codes for lactase, which breaks down lactose. In people who are lactose intolerant, the gene essentially switches off after weaning. However, a mutation known as lactase persistence arose in recent human history that allowed lactase to be produced into adulthood. This trait likely provided a selective advantage to individuals with access to domesticated dairy animals, who consumed the unfermented milk. “Analysis based on the conservation of lactase gene haplotypes indicates a recent origin and high selection coefficients for lactose persistence, although it has not been possible to say whether early Neolithic European populations were lactase persistent… (J. Burger et al., 2006)”