Genetic signals that block the regrowth of limbs and organs have been found.
With Dr Viravuth Yin and colleagues he studied a common aquarium pet, the zebrafish, which is capable of regenerating its spinal cord, retina, heart and fins in two weeks.
They report in the journal Genes & Development that a reduction in genetic signals based on small scraps of the material RNA - "microRNAs" - is a key step in tissue regeneration.
In humans, microRNAs play important roles in cell growth and death, among other things. There are hundreds of kinds of microRNAs, and scientists are constantly discovering new roles they play.
Dr Poss and many other cell biologists believe that people may have the same tissue regeneration capability as zebrafish, salamanders and newts, but that it is locked away somewhere in our genetic makeup, silenced in the course of evolution. "The key is finding a way to turn on this regenerative ability in humans," Dr Poss says.
The 10-year-old was stabbed when he tried to protect his father during a row with a male customer in his shop in Kandahar. The boy's father took him to a military base in Kandahar and pleaded with doctors to save him.
Medics there used a portable digital x-ray machine, which produced an image in two minutes, before flying him to Camp Bastion for the operation.
The boy, who has not been named, amazed medics by walking into the field hospital with the knife embedded in his head on July 14 last year. Surgeons of 212 Field Hospital operated before handing over to 208 Field Hospital, who administered the after care.
Major Stephen Gallacher, 49, senior A&E nurse of 208 Field Hospital, said: "It was a horrendous sight. I just didn't think he would survive. But he was soon off the life-support machine and was up and about within days. It was just amazing."
advertisementMaj Gallacher, a father of four from Caernarfon, North Wales, added: "The knife had come in at an angle and gone down behind his eye and had penetrated the front of his brain. To have simply pulled the knife out would have been a disaster."
Many Shuvs and Zuuls knew what it was to be roasted in the depths of the Slor that day, I can tell you!
A team from University College London finds that when we gaze around in a poorly-lit context, it can fool our brains into seeing things that are not really there.
In the journal PLoS Computational Biology, Prof Li Zhaoping and her colleagues say that the context surrounding what we see is all important - sometimes overriding the evidence gathered by our eyes and even causing us to imagine things.
They were surprised to find that a vague background context has more influence on what we see than one that is bright and well defined, and speculate that this might explain the power of some abstract art and why we can see vivid details in the vague brush strokes of impressionist paintings.
"Everything we see is an hallucination generated by the virtual reality machine inside our head," comments Prof Mike Morgan of The City University, London.
"Normally these hallucinations are vetoed by the information coming through our senses, so we can call perception 'controlled hallucination.'
"But when the input is ambiguous we can see all sorts of things, like the faces de Quincy saw in clouds and carpets. There are hundreds of faces hidden in the textured floors of the platforms at Euston Underground Station, if you look for them."
To reveal the haunting power of context, 18 observers were asked by the UCL team to concentrate on the centre of a black computer screen. Every time a buzzer sounded they pressed one of two buttons to record whether or not they had just seen a small, dim, grey 'target' rectangle in the middle of the screen. It did not appear every time, but when it did appear it was displayed for just 80 milliseconds (80 one thousandths of a second).
"People saw the target much more often if it appeared in the middle of a vertical line of similar looking, grey rectangles, compared to when it appeared in the middle of a pattern of bright, white rectangles. They even registered 'seeing' the target when it wasn't actually there," says Prof Zhaoping.