Wednesday, 28 March 2012

Mapping the gorilla genome helps piece together human evolutionary tree

Original article was sourced from the scientific journal, Nature http://www.nature.com/nature/journal/v483/n7388/full/nature10842.html

Gorillas are humans’ second closest living genetic relatives after chimpanzees, and for a long time, the evolutionary links between humans, gorillas, chimpanzees and orang-utans was somewhat indistinct. “There are four subspecies of gorillas: the eastern lowland gorilla (Gorilla beringei graueri); the mountain gorilla (Gorilla beringei beringei); the western lowland gorilla (Gorilla gorilla gorilla); and the Cross River gorilla (Gorilla gorilla diehl)” (Defenders of Wildlife, 2012).  These creatures’ populations are in great threat of extinction. Their major threats are habitat loss, poaching and diseases such as the ebola virus (Defenders of Wildlife, 2012). 
Figure 1: Direct killing (mostly for the bush meat trade) or hunting (for live animal trade) are major threats facing Gorillas today (CMS, 2009).

 Scientists have already sequenced the genomes of humans, chimpanzees and orang-utans. A group of scientists have now recorded the genome of the last genus of the living great apes and found some unexpected results.
Researchers mapped the DNA sequence of a western lowland gorilla, named Kamilah, and also part-sequences from three other animals. Two from the same sub-species as Kamilah, the western lowland gorilla and one eastern lowland gorilla.  These genes were compared to humans and then of all existing great apes. Their findings were firstly that humans, gorillas and chimpanzees split from their common ancestor around 10 million years ago, and that humans and chimpanzees diverged from each other around 4 million years after that (Science Daily, 2012).  

Figure 2: Phylogeny of the great ape family, showing the speciation of orang-utan, gorillas, chimpanzees and humans. (BioLogos Foundation, 2012)

Another outcome of the study found that 30% of the gorilla genome is closer to humans or chimpanzees than humans and chimpanzees are to each other. More specifically, 15% of the gorilla genome is closer to the human genome than the human genome is to the chimpanzees. Additionally, 15% of the gorilla genome is closer to that of the chimpanzees, than chimpanzees are to humans. However, this similarity is rare in coding genes which has functional differences in gene expression. 

Figure 3: Gibbon, Orangutan, Chimpanzee, Gorilla and Human skeleton drawings (World Press, 2009)
Approximately 500 protein coding genes revealed accelerated evolution with the human, chimpanzee and gorilla line. An example of this is that certain genes involving brain development and hearing have gone through fast, parallel changes in both the gorillas and humans. The gene LOXHD1 was thought to be involved in human hearing, and therefore human speech. This gene showed equal evolutionary change in the gorilla and human. However, gorillas cannot speak. This discovery puts a whole new outlook on what scientists thought they knew about certain human genes (Aylwyn S, 2012)


Figure 4: Gorilla ear (Author unknown, 2010)
Figure 5: Human ear (Hartley, D. 2009)





















As gorilla populations are rapidly declining, scientists are now hoping that the sequence of the gorilla genome will help with conservation of the species, possibly through isolating the gene that is involved in fitness (Aylwyn S, 2012).
The importance of learning as much as possible about the great apes will provide a deeper understanding of human and ape evolution, and also offers more of an appreciation and insight about a time when human existence was primitive. 

References:

  1. Aylwyn S, Julien Y. Dutheil, LaDeana W. et al. 2012. ‘Insights into hominid evolution from the gorilla genome sequence’. Nature. Volume 483, page 169-175, viewed 11th March 2012, < http://www.nature.com/nature/journal/v483/n7388/full/nature10842.html> 
  2. Science Daily, 2012, What Have We Got in Common With a Gorilla? Insight Into Human Evolution from Gorilla Genome Sequence, accessed 11th March 2012   
  3. Smith, K. 2012. Gorilla joins the genome club, NatureNews, viewed 14th March 2012  
  4. Defenders of Wildlife. 2012. Gorilla, accessed 16th March 2012  
  5. CMS, 2009. Gorilla: Conservation Status. Accessed 28th March 2012.  
  6. BioLogos, 2012. Understanding Evolution: Speciation and Incomplete Lineage Sorting. Accessed 28th March 2012.  
  7. World Press, 2009. Quantifying biological success. Accessed 28th March 2012.  
  8. Author unknown, 2010. Ear Modelling. Accessed 28th March 2012.  
  9. Hartley, D. 2009. MIT uses human ear as model for an RF chip. Accessed 28th March 2012.

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