Question

Why might a person's outward appearance not necessarily be an indication of their ethnic background?

Some modern ethnic groups have (white Europeans, Asians) have apparently inherited genes from Neanderthals that may influence resistance to cold temperatures. What types of genes might these be?

Explain the importance of the replacement model in the evolution of the genus Homo?

Answer 1

•Neanderthals were very early (archaic) humans who lived in Europe and Western Asia from about 400,000 years ago until they became extinct about 40,000 years ago. Denisovans are another population of early humans who lived in Asia and were distantly related to Neanderthals.

•Studies have suggested that certain genetic variations inherited from archaic humans may play roles in hair texture, height, sensitivity of the sense of smell, immune responses, adaptations to high altitude, and other characteristics in modern humans.

•researchers from Princeton University now believe, We all likely have a bit of Neanderthal in our DNA. Based on a new computational method They found that modern Europeans, Asians and Americans  inherited about 2% of the genes from Neanderthals.

•the archaeological record shows that Neanderthals and early modern humans coexisted only in Europe and western Asia. Green and colleagues hypothesized that Neanderthals and modern humans came into contact and interbred in the Middle East ∼50–80 KYA, prior to the divergence of modern-day European and Asian populations.

•Green et al. (2010) presented three kinds of evidence in favor of interbreeding.

1.First, they found (using D-statistics, a new measure of genetic similarity introduced in that article) that the three sampled non-African genome sequences (from a French, a Han Chinese, and a Papua New Guinean) are more similar to the Neanderthal sequence than is either of the two sampled African sequences .

2.Second, they identified several haplotypes that are in low frequency in Europeans, absent from Africans, and present in the Neanderthal sequence, which suggests those haplotypes were derived from Neanderthals.

3.Third, they found many more genomic fragments in a European genome than in an African genome that have low divergence to the Neanderthal genome.

•Yang and colleagues found that the doubly conditioned frequency spectrum in Europeans and in East Asians is consistent with Neanderthals , and suggest that there is a gene flow [interbreeding between Asians and Neanderthals ]

•By comparing the geographic locations of individuals from different regions with the archaic ancestry signal (principal components values), East Asian and Native American populations were found to be more similar to archaic hominins compared with European and Central/South Asian populations .Because it is well-known that principal components of modern human genetic variation capture geography to some extent we also computed principal components using modern human genetic variation in Eurasia and found that the top two PCs of differentiation between Europe and East Asia were correlated with the archaic ancestry signal (PC1: rs = 0.138, P < 10−5; PC2: rs = 0.090, P = 0.002). This result suggests that, if separated along the major axes of differentiation between Europe and East Asia, individuals on the eastern end of the spectrum tend to be more similar to archaic human genomes.

•Now let us look on replacement model

•The Replacement model asserts that there was a single origin of Homo sapiens in Africa and that these anatomically modern humans migrated out from Africa and replaced all other less evolved humans throughout Europe and Asia - hence the name, Replacement model. ... In other words, you and I are Homo sapiens.

from above discussion we can conclude that there is a gene flow between Asia and the archaic man . Scientist found the SNP , between them and prooved that they had a genetic flow between them. which help Europeans, Asians to cope up with cold environment.