Friday, 24 October 2014
Sketchy Fact #64: The Clap
Gonorrhea bacteria can pull 100,000 times their own weight, making them the strongest creatures on Earth relative to body size.
Wednesday, 22 October 2014
Epidemiology: How to know when things are safe and when they R-naught
As the
ebola epidemic continues to rage in west Africa and new cases start to pop
up in countries like Germany and the US, people are beginning to pay attention
to the study of how diseases spread through groups. Movies like Contagion and Outbreak give some idea of the work that
gets done when a disease begins to pose a threat, but not many of us really
understand the nuts and bolts of the science known as epidemiology. Where do
diseases come from? How are they spread? Why has the current ebola epidemic proven
to be so difficult to contain if, as we learned a few articles ago, the disease
isn’t actually all that easy to catch? It turns out the answers are as interesting
as the questions.
Where do diseases come from?
How can a
disease like ebola suddenly burst onto the world’s stage? When you stop and
think about it, it doesn’t make a lot of sense. If ebola is so deadly and is
able to spread from person to person the way it has been for the past 10
months, why isn’t it something that is always going on? Well, in the case of
ebola and many other diseases that harm people, the reason is that diseases
have reservoirs where they hide out between epidemics.
When I say "reservoir" I don’t
mean that there is a dam somewhere and behind it is a churning green soup of
ebolavirus. Disease reservoirs are animals that viruses can live within without
causing any ill effects. In the case of ebola, the reservoir is thought to be
fruit bats. The reservoir for influenza is sea birds. The reservoir for plague
is fleas. Every animal out there is a potential host for the next horrifying pandemic. Every so often humans come into contact with these animals in a way
that allows diseases to jump into our bodies, this is called a spillover.
For more on that, check out this great book published last year by David
Quammen. Diseases that spread this way, from animals to people are called
zoonoses (plural of zoonosis) and they make up most diseases you can name.
How do diseases spread?
The spread
of a disease through a group of people depends on a number of things.
Epidemiologists bring a few different factors together to present that
information in a neat and tidy number they call R0 (pronounced
“R-naught” because being British is fun). In its simplest terms R0 is
the average number of healthy people that a sick person will infect while they have
the disease. Ebola has the same R0 as
hepatitis C: 2.
That means that if I had ebola I could expect to infect 2 new people before I
either died or was cured, maybe my wife and my doctor, or a doctor and a nurse. Either way, a couple of you suckers are going down with me. R0’s of other notable viruses include 4 for HIV and SARS, 10 for
mumps, and a whopping 18 for measles.
R0 depends on a few
different things:
the probability of infection after being exposed to an infected person, the
average rate of contact between infected and susceptible people (some people will be naturally immune), and how long
the disease is contagious for. What is working against ebola’s R0 are
the facts that the rate of transmissible contact between people is low (you need to be in
physical contact with a person’s bodily fluids to catch it), and the fact that
the disease is only contagious when a person starts to show symptoms (which
usually isn’t very long… because ebola kills too quickly). Diseases with higher
R0 are able to spread through the air or survive in water.
Why haven't we been able to stop ebola yet?
Aside from
the actual treating of sick people and coordinating quarantines and such,
epidemiologists are also disease detectives. It is their job to determine who
the first person to catch the disease was in an outbreak (the infamous "patient zero") and by
what means it was able to spread. The full story of the current ebola outbreak
can be found in Jeffery E. Stern’s article Hell in the Hot Zone, published earlier this month by Vanity Fair – it is definitely worth
reading.
The Cliff
Notes version is that cutting down the rainforest in West Africa brought people
into closer contact with bats, leading to the spillover. After that, the
international response was swift and well-coordinated, but it was not
communicated well enough. The problem seems to have been that the teams of
doctors and scientists in hazmat suits that rolled into the afflicted villages
did not tell the friends and family of patients what was going on in a way that they could understand and trust. All those
people saw was their loved ones being carried into tents by people in space
suits and disappearing forever. After that people got understandably scared of western doctors. They didn’t
report infections and the disease was able to spread at the same time that health care workers
thought the epidemic was slowing down due to the empty hospital beds all around
them. When the disease finally got to the point where it was impossible to
hide and people started seeking out treatment, it was too late.
Epidemiology
is a very cool field of science that often goes unappreciated. There are
currently thousands of hard working people putting themselves at risk to
contain the situation in Africa, but they need more help. If intervention isn’t
stepped up soon, the rate of new cases of ebola is expected to rise to 10,000 per week, because even with an R0 of
2 the spread is still exponential. If
you are able, please donate to Doctors Without Borders, who are leading the fight against
the spread of the disease. Your money won’t only go towards treating the sick,
it will buy gloves and masks and proper equipment to help keep those doctors as safe as possible.
Friday, 17 October 2014
Sketchy Fact #63: We don't need roads.
If you could drive your car straight into the air at full speed, you would make it to outer space in a little over an hour.
Wednesday, 15 October 2014
5 Organs You Don’t Need
The human
body is a pretty amazing thing. Unless you’re a surgeon or a serial killer you
will probably never fully appreciate all the crazy organs that people have and
the myriad tasks they accomplish every minute of every day. But as well-evolved
as our bodies are, there are a few bits and pieces we could do without. With
that in mind, we thought we would take a trip around the body this week to talk
about some of its most useless organs.
1. Male Nipples
Let’s deal
with male nipples right off the bat. The only reason they exist is because even
the manliest man you will ever meet began life in his mother’s womb as a
female. When the developmental process gets started all babies, boy or girl, follow
the same plan. It is only later that male genes on the Y chromosome kick in and
plant the seeds of beards and all the rest of what makes a man a man. The result is that men end up with
a pair of purely decorative chest ornaments that serve only as a target for
adolescent pain-inducement before the brain is fully developed.
2. Coccyx
You may not
know it, but you have a tail. It is a remnant from when our ancestors used to
run along branches and swing through trees. Back then it aided in balance and
since then it has become essentially a 5th limb for some species of new-world monkeys, allowing them to grip branches and hang hands-free. That is great for the monkeys, bu all it is for most
people is a lump of fused vertebrae tucked inside the skin at the base of our
spines. For an unlucky few it sticks out and makes them self-conscious. It’s
only real function these days is as a dominant scrabble word.
3. Wisdom Teeth
In the land
of long-ago your forebears lived harsh lives. They had to chew tough meat
right off the bone whenever they could get it. They also had to catch that meat and
risk getting a few teeth knocked out in the process. For that reason humans
evolved an extra couple pairs of molars to come in later in life to fill in the
gaps. However, now that we have toothbrushes and the like wisdom teeth
generally do more harm than good. The
most joy they ever bring these days is to the friends of people who just had
them removed.
4. Erector Pili
Aside from
eliciting the occasional chuckle from less mature readers of science blogs, the
erector pili are another part of the body that serves no useful function. These are the organs that cause
your skin to get all bumpy when you’re cold or afraid. Back when we were
covered in body hair, they made that hair stand up to help us hold in extra warmth or to look big and mean. You may have seen an angry dog using its erector pili
to raise the hair on the back of its neck during a barking fit. Since humans aren't typically fur-covered anymore, the effect is a little less dramatic.
5. Plica Semilunaris
Our last
useless organ is so obscure that Microsoft Word thinks it’s a spelling mistake.
It is the plica semilunaris, more common called your third eyelid. It sits in
the inside corner of your eye near the tear duct and you can only really
see it if you pull your eye wide open. It used to protect our eyes while
letting us still see the world when our ancestors lived underwater. Watch a video of a crocodile about to submerge itself and you will see these transparent eye-covers in action.
Unfortunately, in humans they have withered to the point of uselessness,
although it would be really cool if they still worked. Built-in ski goggles
anyone?
Honourable Mention: The Appendix
One organ
you may have expected to find on this list is the appendix; that small dangling
protuberance at the point where your small and large intestines meet. Granted
they do have a tendency to become infected and 1 in 20 people get them removed
with no apparent problems, but your appendix isn’t useless. Recent research has
shown that the appendix is a storehouse for some of the beneficial bacteria we learned
about in a previous article. The bacteria lie in wait until
things go haywire in your large intestine before riding to the rescue. If the
appendix were as useless as everyone used to think, it wouldn’t have hung
around the evolutionary toolshed for 80 million years and involved in countless
other species of animals. So give your appendix the credit it deserves… Unless
it gets infected. Then cut it out like a bad habit.
References:
Friday, 10 October 2014
Sketchy Fact #62: PB&G
In a 1999 book, 250 of the world's greatest minds agreed that peanut butter has no effect on the rotation of the Earth.
Wednesday, 8 October 2014
The Trouble with Tardigrades: The Trials and Tribulations of Nature’s Toughest Animal
Imagine for a moment that you are a hitman for mother nature. It is
your job to find and kill any animal she requests. Obviously some contracts are
going to be easier than others. Taking the life of a grizzly bear or a great
white is going to be a bit more challenging than ending a lamb or grasshopper.
However, even sharks and grizzly bears are easy targets compared to nature’s
toughest creature. Freeze a shark solid in a block of ice and boil a grizzly
bear and your job is pretty well taken care of, but do the same to a tradigrade
and you’re in for a long and frustrating wait.
You may not have ever heard of tardigrades, but they are everywhere you
have ever been. There are billions and billions of them in every environment on
earth. In fact there is a stout branch on the tree of life that contains
nothing but the 1000+ species of these little guys. A tardigrade isn’t a bacteria
or any other kind of those not-quite animals you hear about being everywhere either,
they are honest to goodness animals that you can see with the naked eye… in the
right light.
Tardigrades, also known as water bears for their resemblance to very
tiny pandas, are on average about 1 millimeter long. That is about the size of
the period at the end of this sentence. They are mostly transparent and have
eight stubby legs, each ending in an alien/bear/eagle like claw. They spend
their days sucking water off of moss and feasting on algae with their spear-like mouths. However, unlike most animals that live in
the land of the very small, tardigrades are actually kind of cute in a
monstrous sort of way.
They get their name from the Italian word tardigrada meaning “slow
walker” because unlike most tiny animals that dart around like Carrot Top on
PCP, tardigrades lumber around slowly and pretty clumsily, doing their
tardigrade thing. Tardigrades are a scientists best friend because they are
small and breed quickly. An individual contains about 1000 cells and has a
lifespan of around one year… Unless of course you subject them to the cruelest
kinds of punishment imaginable, then they will live WAY longer.
Indeed, a tarigrade is a very peculiar thing. Leave it alone and it will
lead a pretty uninteresting life, but if you freeze them, dry them out, cook
them, or expose them to radiation you had better be prepared to have your mind
blown. Tardigrades can withstand temperatures from 1 Kelvin (-458 F/-272 C) to
148 C (300 F). They can survive pressures 6 times greater than the deepest
point of the ocean and brush off a dose of radiation 1000 times greater than
what would kill an elephant.
When a tardigrade is thrown into one of these woefully undesireable
situations it pulls off an amazing trick. It can dehydrate it’s body by 97%,
converting water into a sugar called trehalose which prevents cells from
rupturing when they freeze or heat up. When they do this, tardigrades go into a
sort of hibernation, almost entirely shutting down their metabolisms. When
conditions improve, they simply rehydrate and go back to the business of moss
sucking. A tardigrade can survive in its hibernating state for at least ten
years but possibly for more than a century.
As if all of this wasn’t enough to bestow them with the honour of nature’s
most indestructible creature, tardigrades are the only animals we know of that
have survived the vacuum of space. In 2007 NASA sent a team of tardigrades
along with a few astronauts up into orbit. They opened the airlock and set the
tardigrades floating in space for ten days where they were exposed to extreme
cold, extreme heat, and intense radiation. Apparently the tardigrades just treated
this as a vacation because when they were brought back to earth they woke
themselves up from an extended nap and just went on living. A few even
reproduced.
This is all pretty amazing but why does it matter? We can get
jealous of tardigrades until the cows come home but it doesn’t help us much,
does it? Actually, tardigrades provide good evidence for a long held idea in
science called panspermia which is meant to explain where life on earth came
from. It is thought that life may have started elsewhere in the universe and
been spread by collisions with meteors. When a meteor hits a planet it sends
pieces of that planet rocketing into space and drifting through the void. If
creatures like tardigrades are tough enough to survive such a trip and land on
another planet, life might be a pretty common feature of the universe. Tardigrades themselves might even be an alien life form.
That is real gift that tardigrades give us. Through their survival of
nearly everything, including all 5 mass extinction events so far on earth,
through their uncountable numbers on earth, and through their ability to travel
in space tardigrades provide strong evidence that we aren’t alone in the
universe… And if you’re reading this in a mossy forest alcove you’re really not alone.
References:
Friday, 3 October 2014
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