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Lucy’s Legs: The software showing us how our ancestors walked

Based on a presentation by Dr Karl Bates (UoL Institute of Ageing and Chronic Disease):
“Biomechanics – understanding the relationship between anatomy and function”

Happy Sunday, everyone! Hope you’re having a good weekend! Here we have a description of the 2nd piece of research presented at the evening of seminars I attended last week. Enjoy!

Now, the first thing you might be wondering after reading the title is, what exactly is the field of Biomechanics? I’ll admit that I’d never heard of it before this talk! Essentially, it’s the study of an organism’s moving parts in order to understand how their arrangement relates to their function. Dr Bates’ research group is looking at human legs, studying the relationship between their morphology (i.e. the shape and arrangement of muscles, bones and tendons etc) and the way humans walk.

The group wants to find the muscle activation pattern that produces the fastest, or most energy-efficient, way of running. They’re carrying out their work using a technology called ‘Evolutionary Robotics’. This involves a computer program that uses a mathematical model (code for ‘maths 99% of us can’t hope to grasp’!) with values for every single muscle in the pair of legs.

An example of a Gait Lab - this one is at Strathclyde University. The test subject walks/runs between the cameras with sensors attached to their legs so that a computer can recreate the motions they pick up. This is similar to the technology used to create film characters like Gollum in The Lord of the Rings.

An example of a Gait Lab – this one is at Strathclyde University. The test subject walks/runs between the cameras with sensors attached to their legs so that a computer can recreate the motions they pick up. This is similar to the technology used to create CGI film characters like Gollum in The Lord of the Rings. (Photo Credit: Strathclyde University)

The system takes recordings of a human running through the group’s ‘gait lab’ and matches the pattern of muscle activation it sees.  It then tests every possible combination of muscle contraction strengths and timings as it attempts to create the most energy-efficient version of the running motion it saw.

Sounds relatively straightforward – leave your computer running for a while and let it come back with a neat and tidy result, right? Well….no. There are millions and millions of possible combinations that the computer needs to work through. As such, they need one impressively powerful computer, and it still takes ages!

Brilliantly, the program builds a pair of virtual human legs, including tissues, joints and tendons, so you can see how its current optimum equation works. At this point, Dr Bates showed us a ridiculous video of a pattern the computer suggested early on. The legs rotated round the hips in 360° turns, moving along like some kind of grotesque ball! One of the latest suggestions shows the legs moving normally for a while…before falling over! But it is getting there…

Now, this is all well and good, but what’s the point? Well, once the computer program has mastered the leg movement, the group can use it to understand the changes humans undergo as we age. We know that we lose muscle mass and gain fat, meaning that our bodies can’t operate in exactly the same way as when we were young. But what we don’t know is in what ways our bodies have to compensate for these changes.

Dr Bates said that, once they know how the legs move and which muscles are needed, they can start playing around with the anatomy in a way they couldn’t do in real life. They can, for example, change tendon lengths and muscle masses in a virtual pair of legs to reflect an older person’s physiology. This will allow them to see how energy efficiency changes during a person’s life-time and how different parts of the legs must change to cope with, for example, reduced muscle mass. This will give us a greater understanding of the pressures our bodies come under as they age.

« Lucy » skeleton (AL 288-1) Australopithecus ...

Casts of Lucy’s fossilised remains. These bones were all the team had to work with! (Photo Credit: Wikipedia)

Model of the australopithecus Lucy in the muse...

A very happy-looking model of what we think Lucy looked like, at the Museum of Barcelona (Photo Credit: Wikipedia)

The group’s work will also help us understand more about how we have evolved as a species. A really interesting application of the group’s work so far has been to solve the controversy over how one of our ancient ancestors – Australopithecus afarensis – walked. The best-known fossil of the species is a partial skeleton, which has been named Lucy!

Lucy is 3.2 million years young and, despite how little of her was found, researchers have estimated that the lengths of Lucy’s humerus and femur leg bones are right in-between the lengths seen in humans and chimps. So, the question is, did she walk upright like humans or using her arms like chimps?

The group used their computer program to simulate Lucy walking in both ways. They worked out that it was far more energy-efficient for her to walk upright, given her bone structure. As animals very often adapt to be more energy-efficient, it seems likely that Lucy and her Australopithecus afarensis brethren walked upright like us.

To confirm this, the group compared the heel pressure Lucy was predicted to exert when walking upright with the pressure her preserved footprint implied. The two pieces of evidence matched. So, thanks to this research and the group’s remarkably clever computer software, we now know that 3.2 million years ago our ancestors were already walking upright. This suggests that we started walking upright when we were still living in the trees rather than when we’d moved down to the ground, as we previously thought!

I think this is a fascinating piece of research and the findings and potential applications are incredible, offering compelling evidence for how our ancestors have evolved. I look forward to hearing more about the group’s findings as their research continues.

Next up in this mini-series, we have a description of how ‘Personalised Medicine’ will work and how far away it is from being a reality. Come back next week for that one. Till then, have a great few days!

 
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Posted by on June 30, 2013 in Biology

 

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Why is Snake Venom so variable?

Saw-scaled Viper (Echis carinatus)

Saw-scaled Viper (Echis carinatus) (Photo credit: Frupus)

Based on a presentation by Dr. Wolfgang Wüster (Bangor University) – 12/03/13

I hate snakes. I’m just going to say it from the start; they scare the living daylights out of me. I’d have been living with one if my girlfriend hadn’t noticed the colour drain from my face when she mentioned buying one. And yet, for reasons I cannot explain, I went along to a seminar yesterday all about venomous snakes! I’m glad I did though – Dr. Wolfgang Wüster talked about them with great energy and enthusiasm, getting quite a few laughs along the way, and, most importantly, piquing the entire lecture theatre’s interest. I found the talk so engaging that I’ve decided to share what I learned here.

Snake venoms are mixtures of toxins, usually consisting of tens to hundreds of the poisonous proteins. This obviously allows for a great degree of variation in nature as different venoms contain different combinations of toxins and quantities thereof. As you’d expect, lots of different species of snake have different toxins; however, the variation can go all the way down to differences between members of the same species. In fact, in some species, an adult’s venom can be different to its venom as an infant. This wide range of venoms has an equally diverse range of effects on prey, resulting in paralysis, haemorrhages, and massive cell death and tissue damage, amongst other things. Upon explaining this in the talk, Dr. Wüster took great pleasure in showing some truly disgusting images – remember; I go through the pains of Science so you don’t have to!

English: Most common symptoms of any kind of s...

Common symptoms of any kind of snake bite poisoning (Photo credit: Wikipedia)

The main question of the talk was that of what causes this variation in venom composition. It’s probable that this all depends on what individual venoms are used for, which, in the majority of cases is overpowering and killing prey. Diet in snakes is an example of a ‘selective pressure’. This is where something affects the survival of a population, thus encouraging evolution of that population to overcome the stress.

Diet, as a selective pressure, acts upon many characteristics of venom. For example, the volume of venom stored in a snake’s glands is usually only enough to kill enough prey to survive. As such, snakes requiring a greater food intake or those that kill larger prey will produce more venom than those that consume less food. The overriding reason for this is that producing venom requires energy, so the minimal amount necessary is made and used.

Dr. Wüster’s group saw an interesting example of this in a model system of 4 species of Saw-scaled Vipers. Whilst most snakes eat vertebrates (animals with a backbone), these vipers also eat arthropods (invertebrates with exoskeletons and segmented bodies, such as scorpions and spiders). The 4 species differ greatly in the ratios of arthropods and vertebrates that they eat, yet all 4 species take 2 to 3 bites to kill scorpions, taking their time to see how much venom is necessary to subdue their prey. This may be evidence of economy of usage of venom, meaning that these model organisms have evolved to favour potent, rather than voluminous, venom to reduce the amount required.

Anatomy of a venomous snake's head (Photo Credit: How Stuff Works)

Anatomy of a venomous snake’s head (Photo Credit: How Stuff Works)

Prey resistance also plays a role in determining the volume of venom a snake produces, as well as the potency of that venom. For example, Moray Eels that live in the same regions as Sea Snakes have evolved resistance to the snakes’ venom. As a direct consequence of this the snakes have evolved to produce and release more of it to compensate.

In conclusion, Dr. Wüster presented compelling evidence that venom composition differs based on dietary requirements. Different combinations of toxins affect different preys, and different snakes need their venoms to have different harmful effects. The ‘arms race’ that develops from predator-prey relationships, whereby the prey evolves to resist the venom and the snake evolves to counteract this, also drives diversification. Finally, using venom economically seems to be a very important factor in these predators. Dr Wüster explained that future work would take a detailed look at the genetics behind venom variation, studying the genes encoding toxins and the variation that exists therein. I, for one, look forward to hearing about their findings, even if it does mean spending more time looking at pictures and videos of snakes…

 
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Posted by on March 13, 2013 in Biology

 

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