How humans got their hands: Researchers reveal genetic mutation left us with just five fingers - and say they are similar to fish fins
- Study in August found fin rays and human fingers share same two genes
- Our ancestors had more than 5 per hand, which raises many questions
- Recently a team genetically engineered mice to grow 7 digits per paw
- Results suggest a mutation inside our ancestors genes produced 5 digits
A recent study identified two genes responsible for the formation of both fin rays and human fingers, which 'clearly establishes a molecular link' between them.
But fossil records show our ancestors were polydactyl, meaning they had more than five digits per hand, which has left experts wondering why we only have five.
Now, researchers have discovered that this major morphological change did not occur through the addition of new genes, but from a mutation that transpired within them.
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![A recent study identified two genes responsible for the formation of both fin rays (right) and human fingers. But fossil records show our ancestors were polydactyl, meaning they had more than five digits per hand, which has left experts wondering why we only have five](https://i.dailymail.co.uk/i/pix/2016/10/06/21/392C3FE900000578-0-image-a-2_1475785584811.jpg)
A recent study identified two genes responsible for the formation of both fin rays (right) and human fingers. But fossil records show our ancestors were polydactyl, meaning they had more than five digits per hand, which has left experts wondering why we only have five
In Augusts, a team from the University of Chicago revealed that not only do our hands have an evolutionary connection to bats, but fish fins as well.
The researchers discovered that both fin rays and our fingers contain the same two genes – hoxa11 and hoxa13.
Although exciting, a team of experts at Montreal University point out that the transition was not accomplished overnight.
One observation in particular caught the attention of the team:
'During development, in mice and humans, the hoxa11 and hoxa13 genes are activated in separate domains of the limb bud, while in fish, these genes are activated in overlapping domains of the developing fin,' said Marie Kmita, associate research professor in the Department of Medicine at Montreal University.
In order to understand the significance, the team genetically engineered mice to grow seven digits on each paw using fish-type regulation of the hoxa11 gene.
The team discovered the sequence of DNA responsible for the transition between fish- and mouse-type regulations for the hoxa11 gene.
![In Augusts, a team from the University of Chicago revealed that not only do our hands have an evolutionary connection to bats, but fish fins as well. The researchers discovered that both fin rays and our fingers contain the same two genes – hoxa11 and hoxa13](https://i.dailymail.co.uk/i/pix/2016/10/06/21/392C011C00000578-0-image-a-1_1475785546608.jpg)
In Augusts, a team from the University of Chicago revealed that not only do our hands have an evolutionary connection to bats, but fish fins as well. The researchers discovered that both fin rays and our fingers contain the same two genes – hoxa11 and hoxa13
'It suggests that this major morphological change did not occur through the acquisition of new genes but by simply modifying their activities,' added Dr. Kmita.
This study reveals that malformations during fetal development are not only due to mutations in the genes and may come from mutations in sequences of DNA known as regulatory sequences.
'At present, technical constraints do not allow for identifying this type of mutation directly in patients, hence the importance of basic research using animal models', said Dr. Kmita.
How this evolution occurred is a fascinating question that goes all the way back to the work of Charles Darwin, who discovered humans share a common ancestor that grew limbs with digits with moles, horses, porpoises and bats.
'What can be more curious,' he asked, 'than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include similar bones, in the same relative positions?'
Darwin may have been down the right path to discovering our hands began as fins, but the lack of cutting-edge technology held him back.
Lucking, today's scientists have access to high-tech biological tools and are capable of discovering other similarities that were once overlooked, reports the New York Times.
![Now, a separate team found that that malformations during fetal development are not only due to mutations in the genes and may come from mutations in sequences of DNA known as regulatory sequences](https://i.dailymail.co.uk/i/pix/2016/10/06/22/392C012800000578-0-image-a-12_1475787762460.jpg)
Now, a separate team found that that malformations during fetal development are not only due to mutations in the genes and may come from mutations in sequences of DNA known as regulatory sequences
'When I first saw these results you could have knocked me over with a feather,' said Neil Shubin, lead author of the study and professor at the University of Chicago, regarding the findings in August.
'For years scientists have thought that fin rays were completely unrelated to fingers and toes, utterly dissimilar because one kind of bone is initially formed out of cartilage and the other is formed in simple connective tissue.'
'Our results change that whole idea. We now have a lot of things to rethink.'
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