foxp2 and neanderthals

8/2/2019 FOXP2 and Neanderthals

http://slidepdf.com/reader/full/foxp2-and-neanderthals 1/12



Introduction• Homo Neanderthalensis andHomo Sapiens shared a commonancestor approximately 400,000

years ago.

• Neanderthals display distinctive physicalcharacteristics and evolved mainly in Europe and

Western Asia.

• Modern humans are thought to have evolved in Africa and then spread to other parts of the world.



Introduction - FOXP2 and Language• No other existing animals have the same capacity for language as Homo

sapiens. Therefore, knowing when and under what evolutionary pressures our capacity for language evolved is of great interest.

• FOXP2 is the only gene known to have a specific role in the development

of language and speech.

• Inactivation of one copy of FOXP2 leads to deficits in orofacialmovements and linguistic processing similar to those seen in individuals with adult-onset Broca’s aphasia.

Broca’s aphasia = damageto the Broca’s area of the brain causing an inability to produce fluent speech.



• FOXP2 is among the 5% most conserved proteins in

mammals. But...

• Two amino acid substitutions (located in exon 7)have been fixed in the human lineage since the split

with chimp common ancestor.

• Analysis using human diversity data around exon 7suggests that a recent selective sweep occurred

(ending within last 200,000 years).

• This suggests that the two substitutions areassociated with the rise of modern language ability.



Aim and Methods

AIM: To analyse genotype of Neanderthals at the twosubstitution positions in exon 7 (nucleotide positions 911 and 977).

They used PCR to amplify DNA from ancient remains.

They combined the control primers with different primers forthe gene – and performed multi step multiplex PCR.

Partial sequence alignment of FOXP2 Gene. The three primer pairs used to retrievethe two substitutions from the Spanish Neandertals.



Not all the control primers yielded products – because of such a smallamount of DNA. But:

• They found that the FOXP2 allele in the Neanderthal samples wasthe same as that in modern humans (they share the same twosubstitutions). Which previously was shown to have been subject toa selective sweep.

• This sequence variant is a G to T substitution, not commonly associated with ancient DNA damage, therefore likely to represent agenuine allele present in the Neandertals.

Results and Discussion



There are three possible explanations for this:

1. Gene flow between Neanderthals and HomoSapiens.

2. The FOXP2 haplotype was present in thecommon ancestor and then was later positively selected for in humans after their divergencefrom Neanderthals.

3. The selective sweep occurred earlier thanpreviously thought – about 300,000-400,000 years ago.



1. Gene flow between Neanderthals and Homo Sapiens.

However, neither the maternally inherited mtDNA nor thepaternally inherited Y chromosome shows evidence of gene flow from modern humans into Neandertals or of subsequentcontamination of their remains. Other autosomal variation testsfailed to detect any gene flow.

2. The FOXP2 haplotype was present in the commonancestor and then was later positively selected for inhumans after their divergence from Neanderthals.

The relevant haplotype needs to be at a considerable frequency inthe ancestral population in order to obtain the high frequencies inNeandertals. However, the higher the variant frequency beforepositive selection, the less likely it is to detect a signature of aselective sweep. Hence, this scenario is unlikely.



3. The selective sweep occurred earlier than previously thought – about 300,000-400,000 years ago.

Given a divergence time of chimpanzees and humans(6.5 million years), the fixation of the sweep would have

occurred within the last 260,000 years. Otherevolutionary factors could further increase the varianceon these time estimates, making it possible that thesweep started or occurred in the common ancestralpopulation of Neandertals and modern humans.

This is the most likely

foxp2 and neanderthals

Documents