1. Atom
Count
It is hard to grasp just how small the atoms that make up
your body are until you take a look at the sheer number of them. An adult is
made up of around 7,000,000,000,000,000,000,000,000,000 (7 octillion)
atoms.
2. Fur
Loss
It might seem hard to believe, but we have
about the same number of hairs on our bodies as a chimpanzee, it's just that
our hairs are useless, so fine they are almost invisible. We aren't sure quite
why we lost our protective fur. It has been suggested that it may have been to
help early humans sweat more easily, or to make life harder for parasites such
as lice and ticks, or even because our ancestors were partly aquatic. But
perhaps the most attractive idea is that early humans needed to co-operate more
when they moved out of the trees into the savanna. When animals are bred for
co-operation, as we once did with wolves to produce dogs, they become more like
their infants. In a fascinating 40-year experiment starting in the 1950s, Russian
foxes were bred for docility. Over the period, adult foxes become more and more
like large cubs, spending more time playing, and developing drooping ears,
floppy tails and patterned coats. Humans similarly have some characteristics of
infantile apes – large heads, small mouths and, significantly here, finer body
hair.
3. Red
Blooded
When you see blood oozing
from a cut in your finger, you might assume that it is red because of the iron
in it, rather as rust has a reddish hue. But the presence of the iron is a
coincidence. The red colour arises because the iron is bound in a ring of atoms
in haemoglobin called porphyrin and it's the shape of this structure that
produces the colour. Just how red your haemoglobin is depends on whether there
is oxygen bound to it. When there is oxygen present, it changes the shape of
the porphyrin, giving the red blood cells a more vivid shade.
4. DNA
Going Viral
Surprisingly, not all the
useful DNA in your chromosomes comes from your evolutionary ancestors – some of
it was borrowed from elsewhere. Your DNA includes the genes from at least eight
retroviruses. These are a kind of virus that makes use of the cell's mechanisms
for coding DNA to take over a cell. At some point in human history, these genes
became incorporated into human DNA. These viral genes in DNA now perform
important functions in human reproduction, yet
they are entirely alien to our genetic ancestry.
5. Without
Bacteria
On sheer count of cells, there is more
bacterial life inside you than human. There are around 10tn of your own cells,
but 10 times more bacteria. Many of the bacteria that call you home are
friendly in the sense that they don't do any harm. Some are beneficial. In the
1920s, an American engineer investigated whether animals could live without
bacteria, hoping that a bacteria-free world would be a healthier one. James
"Art" Reyniers made it his life's work to produce environments where
animals could be raised bacteria-free. The result was clear. It was possible.
But many of Reyniers's animals died and those that survived had to be fed on
special food. This is because bacteria in the gut help with digestion. You
could exist with no bacteria, but without the help of the enzymes in your gut
that bacteria produce, you would need to eat food that is more loaded with
nutrients than a typical diet.
6. Eyelash
Invaders
Depending on how old you are,
it's pretty likely that you have eyelash mites. These tiny creatures live on
old skin cells and the natural oil (sebum) produced by human hair follicles.
They are usually harmless, though they can cause an allergic reaction in a
minority of people. Eyelash mites typically grow to a third of a millimetre and
are near-transparent, so you are unlikely to see them with the naked eye. Put
an eyelash hair or eyebrow hair under the microscope, though, and you may find
them, as they spend most of their time right at the base of the hair where it
meets the skin. Around half the population have them, a proportion that rises
as we get older.
7. Photon
Detectors
Your eyes are very sensitive,
able to detect just a few photons of light. If you take a look on a very clear
night at the constellation of Andromeda, a little fuzzy patch of light is just
visible with the naked eye. If you can make out that tiny blob, you are seeing
as far as is humanly possible without technology. Andromeda is the nearest
large galaxy to our own Milky Way. But "near" is a relative term in
intergalactic space – the Andromeda galaxy is 2.5m light years away. When the
photons of light that hit your eye began their journey, there were no human
beings. We were yet to evolve. You are seeing an almost inconceivable distance
and looking back in time through 2.5m years.
8. Sensory
Tally
Despite what you've probably been told, you
have more than five senses. Here's a simple example. Put your hand a few
centimetres away from a hot iron. None of your five senses can tell you the
iron will burn you. Yet you can feel that the iron is hot from a distance and
won't touch it. This is thanks to an extra sense – the heat sensors in your
skin. Similarly we can detect pain or tell if we are upside down. Another quick
test. Close your eyes and touch your nose. You aren't using the big five to
find it, but instead proprioception. This is the sense that detects where the
parts of your body are with respect to each other. It's a meta-sense, combining
your brain's knowledge of what your muscles are doing with a feel for the size
and shape of your body. Without using your basic five senses, you can still
guide a hand unerringly to touch your nose.
9. Real
Age
Just like a chicken, your
life started off with an egg. Not a chunky thing in a shell, but an egg
nonetheless. However, there is a significant difference between a human egg and
a chicken egg that has a surprising effect on your age. Human eggs are tiny.
They are, after all, just a single cell and are typically around 0.2mm across –
about the size of a printed full stop. Your egg was formed in your mother – but
the surprising thing is that it was formed when she was an embryo. The
formation of your egg, and the half of your DNA that came from your mother,
could be considered as the very first moment of your existence. And it happened
before your mother was born. Say your mother was 30 when she had you, then on
your 18th birthday you were arguably over 48 years old.
10. Optical
Delusion
The picture of the world we "see" is
artificial. Our brains don't produce an image the way a video camera works.
Instead, the brain constructs a model of the world from the information
provided by modules that measure light and shade, edges, curvature and so on.
This makes it simple for the brain to paint out the blind spot, the area of
your retina where the optic nerve joins, which has no sensors. It also
compensates for the rapid jerky movements of our eyes called saccades, giving a
false picture of steady vision.But the downside of this process is that it
makes our eyes easy to fool. TV, films and optical illusions work by misleading
the brain about what the eye is seeing. This is also why the moon appears much
larger than it is and seems to vary in size: the true optical size of the moon
is similar to a hole created by a hole punch held at arm's length.
Source :
http://www.theguardian.com/
