Two competing theories seek to explain the rare phenomenon of conjoined twins. 

The first and oldest theory is known as fission, in which the first cell divisions of the fertilised egg do not result in complete separation of the twins to begin with.

A more recent and more widely accepted contradicting theory, fusion, asserts that two separate embryos form but are rejoined as groups of similar stem cells on either body find each-other and fuse the twins together. 

It’s curious how radically different and symmetrical theories like this can exist. 


How a wound heals itself

Our skin is the largest organ in our bodies, with a surface area of about 20 square feet in adults. When we are cut or wounded, our skin begins to repair itself through a complex, well-coordinated process. Sarthak Sinha takes us past the epidermis and into the dermis to investigate this regenerative response.

View full lesson:

Lesson by Sarthak Sinha, animation by Karrot Animation.

By: TED-Ed.

usmblida09 asked:

I wonder if someone is born in space and live his childhood and adulthood there will he be taller than the one who born in earth ?? Because of the gravity?? Sorry for my english i'm not American

Logically it makes sense. I found an article that does discuss this.

Here’s a couple of excerpts:

According to NASA, most astronauts grow about 2 inches while they’re in space because the reduced gravity causes the fluid between vertebrae to expand. They lose the height within 10 days of returning to Earth’s crushing gravity. Because of the growth, NASA uses space suits that have extra room to accommodate the additional height.


Mars settlement-proponent Robert Zubrin has theorized that children born on other planets with lower gravity, like Mars, which has just one-third of Earth’s gravitational pull would in fact grow taller by a few inches than they would have on Earth. While genes inherited from their parents wouldn’t change, the spine could elongate more than on Earth. 

I don’t know how pronounced growth would be in zero gravity vs low gravity, or if healthy humans can even be born in space (a lot of biological processes require gravity to work properly).


Varied carpet beetle (Anthrenus verbasci)

The varied carpet beetle is a 3 mm-long beetle belonging to the family Dermestidae. This beetle can be a serious household pest and a pest in natural history museums, where it can damage biological specimens. While adults are pollen grazers, larvae feed on natural fibers and can damage carpets, furniture, clothing and insect collections. This species is present in most of Europe, in East Palearctic ecozone, in the Near East, in the Nearctic ecozone and in North Africa.

photo credits: wiki, wiki, Aka

Sam’s Note: I have for years been expressing my theory that the brain and thought has the potential to affect DNA and gene expression. I got more than a few comments by people about how this was new age nonsense. Well, I stand vindicated. This of course is only the first baby step in the process.

Brainwaves from human participants activated a tiny light which had been implanted in mice.

This LED then activated light-sensitive genes which had been genetically engineered to respond in this way.

The authors report that the technology could one day be used to control pain management or pre-empt epileptic seizures.

Though they noted that this paper was a proof of concept and that any potential therapeutic applications were still a long way off.

Senior author of the work, Martin Fussenegger at ETH Zurich in Switzerland, said it was a huge step forward.

Science fiction

"At first you may ask why should I think something and then control my genes? I could push a button and [also] induce the LED.

"The reason is, we’ve designed it for potential application for locked-in patients who can no longer communicate with the outside world other than with their mental activities and brainwaves.

"This sounds like science fiction but it’s an obvious interconnection of different technologies."


Researchers at Monterey Bay Aquarium capture the first video of the Black Seadevil, Melanocetus sp.


Isn’t the deep sea so fascinating? Scientists from Monterey Bay Aquarium Research Institute have captured what’s thought to be the first-ever footage of the ‘black seadevil’ fish

This fish is known as Melanocetus, and it lives in the deep dark waters of the Monterey Canyon. MBARI’s ROV Doc Ricketts observed this anglerfish for the first time at 600 m on a midwater research expedition in November 2014. It looks quite menacing, but it is actually quite tiny, and is only 9cm (around three inches) long.

Little is known about this fish. Male black seadevils have a much shorter life span than females, and are much tinier in comparison. Their sole purpose is to attach themself to a female, living as a parasite. 

Columbia Engineers Grow Functional Human Cartilage in Lab

Full section of a tissue construct with cartilage at the top and bone substrate underneath. The blue stain marks proteoglycan, one of the two key components of cartilage, and red marks the nuclei of the cells.


How the Ichthyosaur Got Its Fins

Have you ever wondered how aquatic reptiles evolved? No? Why not? Regardless, a new fossil discovered in 2011 is shedding light on these questions [1].

Ichthyosaurs are a class of extinct reptiles that ruled the oceans 250 million years ago [2]. Some were as large as blue whales. However, their evolution from the reptilian common ancestor has posed a problem: reptiles evolved on land while ichthyosaurs were ocean dwellers. The intermediary evolutionary steps have been a mystery. 

The mystery remained until 2011, when a fossil found in China showed what is believed to be a proto-ichthyosaur. This transitional specimen, with flippers for forelimbs and small hindlimbs, suggests that the link between ichthyosaurs and reptiles was a sea dwelling animal in the process of evolving into what would become the terrifying apex predators of the sea.

The Cartorhynchus lenticarpus [3] fossil (loosely translated as “short snout, flexible wrist”), shows that ancestral ichtyosaurs were aquatic, although they still shared traits in common with early terrestrial reptiles.

Paleontologists believe that this shows that ichthyosaurs evolved from reptiles that were already primarily aquatic, and that the old theory of walking semi-aquatic sea dinosaurs must therefore be incorrect.

The more we learn about the specifics of the history of life on earth, the more complete the picture we can put together of the origins of the spectrum of modern biodiversity will be.


[1] Perkins, S. How the ichthyosaur got its fins. Science News, November 5 (2014).

[2] Ichthyosaur Wikipedia page.

[3] Dell’Amore, C.   First Amphibious “Sea Monster” Found; Fills Evolutionary Gap. National Geographic, November 5 (2014).


QiGong introduction video (This is really good):

Bioelectromagnetics is the scientific study of electromagnetic fields in biological creatures. There are over 8,600 species of animals that can detect electromagnetic fields. Most of us know that birds travel by sensing the earth’s magnetic field and eels can electrocute in self defense, but what about humans?

Consider how strange it is that something as seemingly non-physical as the thoughts in your mind can cause you to walk and speak. Our entire body communicates to itself in a variety of complex ways including electromagnetic fields. What if we could learn to manipulate these typically involuntary actions within our body?

The 4,000-year-old teaching of Qigong (A.K.A. Chi Kung) is an ancient scientific exploration of harnessing the energies flowing throughout the human body. Qigong translates from Chinese to, “Life Energy Cultivation”. Moving the body in specific ways, practicing breathing exercises, and developing a healthy mind are all disciplines of qigong. It is used to increase health, for martial arts training, and as a type of meditation.

Perhaps the most famous Qigong master is John Chan, (A.K.A. Dynamo Jack). The BBC documentary about Mr. Chan has become a YouTube sensation. In the film, scientists from America and Europe come to study his seemingly magical abilities. Mr. Chan seems to be able to manipulate his body’s various electromagnetic fields to produce an electric current. In one scene he even lights a newspaper on fire with nothing but his natural energy… is this amount of control over our body’s energy really possible?!

John Chan video:

Harvard scientists study monks who can drastically raise their body temperature: