Nitin Verma’s Blog

Human and chimp genomes reveal new twist on origin of species

Advertisements

Previous molecular genetic studies have focused on the average genetic difference between human and chimpanzee. By contrast, the new study exploits the information in the complete genome sequence to reveal the variation in evolutionary history across the human genome. In theory, scientists have long known that some genomic regions must be ‘older’ than others, meaning that they trace back to different times in the common ancestral population that gave rise to both humans and chimps (see Graphic). But, the new study is the first to actually measure the range of ages. It gave three surprising results:

* the time of from the beginning to the completion of divergence between the two species ranges over more than 4 million years across different parts of the genome. This range is much larger than expected.

* the youngest regions are unexpectedly recent — being no more than 6.3 million years old and probably no more than 5.4 million years old. This finding implies that human-chimp speciation itself is far more recent than previously thought.

* if one looks only at the X chromosome, it almost entirely falls at the lower end of the time frame. In fact, the average age of the X chromosome is ~1.2 million years “younger” than the average across the 22 autosomal (non-sex) chromosomes.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s