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Friday, July 21, 2006

Stem Cell Veto

Okay, I'm a day and a half late in writing about this on my blog, but I still want to comment on it (You can read a few of my initial reactions in the comments over at TerrapinTables). It just really, really pisses me off that Bush has vetoed this law.

Here's the analogy I thought of to explain it. Imagine you see somebody fall into a flooded river (to really pull at your heart strings, you can imagine it's your own child). This river's pulling them away pretty fast. There's a guy on a bridge down stream with a rope. Now, if he throws the rope, there's no guarantee that the person in the river will be able to get it and hold on. And, there's always the possibility that the person may get rescued by someone else. But what would you think if the person on the bridge decided to not throw the rope at all?

That's basically what Bush just did. Embryonic Stem (Es) cells are not a guaranteed cure, and there are other lines of research that may lead to treatments for some of the diseases that currently look like they may be treated by ES cells, but why would somebody decide to maintain a ban on such a promising avenue of research?

And this isn't just some hypothetical, intellectual excercise. There are millions of people suffering from diseases and conditions for which ES cells might lead to a viable treatment. How many of them are going to die or suffer needlessly, because he vetoed this bill. If Bush went around randomly killing a person every day for the rest of his time in office, we'd call him a murderer. But if he vetoes a bill that in the end will lead to even more people's deaths because of lack of treatments, we call it politics.

Finally, this whole thing is asinine, because the bill proposed using embryos that were slated for destruction, already. These embryos are going to be flushed down the toilet, whether or not this bill was passed. Why not use them for research before that happens? What a f-in' waste.

Friday, July 14, 2006

Physical Comparison of Humans to Other Animals

Not too long ago, I made a blog entry, Request for Information - Physical Comparison of Humans to Animals I actually did receive some feedback in the form of e-mail, which inspired me to do more research. In the course of which, I found the paper, Differential scaling of locomotor performance in small and large terrestrial mammals, written by Jose (Pepe) Iriarte-Diaz, which was published in the JOURNAL OF EXPERIMENTAL BIOLOGY, 205 (18): 2897-2908 SEP 2002. Anyway, as part of his research into animal locomotion, he had compiled a large set of data of mammal max running speeds along with their body mass and length. This was exactly the type of thing I was looking for in order to characterize how humans compare to other animals.

To recap what it was that got me interested in this in the first place - After years of watching nature documentaries on PBS and the Discovery Channel, you get the impression that humans are pathetic when compared physically to other animals, and that our success was due mainly to our big brains and cleverness. While I'm not arguing against the adaptablity those attributes have given us, about a year ago, I read about a study called "Endurance running and the evolution of Homo", written by Dennis M. Bramble & Daniel E. Lieberman (Nature 432:345-352), comparing humans to other animals in endurance running, and we actually compare quite favorably.

There is a very good summary of the study by PZ Meyers on his Pharyngula Arhcive, and another good one at the UCI Biomechanics site.

Since the above two pages cover the article very well, I won't go into it in much detail. But to give what I think is the "money shot" from the paper, below is a graph showing human running speeds compared to another good long distance runner, horses:

Horse/Human Running Speed Comparison
Comparative ER performance in humans and quadrupeds. Range of speeds for human ER and sprinting, and minimum trot (Tm), preferred trot (Tp), trot–gallop transition (T–G), preferred gallop (Gp), and maximum sustained gallop (Gms) for ponies (ref. 26), and predicted for quadrupeds of 65 and 500 kg (ref. 25). Also indicated is Gld, the optimal long distance (,20 km), daytime galloping speed for horses (ref. 27). Note that quadrupeds sprint at speeds above Gms.

And here's a quote from PZ Meyers on his blog entry that I thinks puts our endurance running capabilities into good perspective, "Human ER [endurance running, i.e. still aerobic] speeds fall between 2.3 m s-1 (I must be somewhere around there) and 6.5 m s-1 (for an Olympic class marathoner), with typical speeds for a moderately fit jogger of 3.2-4.2 m s-1. In comparison, the trotting speed of a horse is about 3.1 m s-1, and once they hit 4.4 m s-1, they break into an anaerobic gallop. Over long distances, the average speed sustained by a horse is about 5.8 m s-1—which means that a well-trained, conditioned human being can keep up with or even outrun a horse if the race is sustained long enough."

So, as far as long distance running goes, humans can hold their own pretty well. But the popular sentiment seems to be that we're still lousy as far as sprinting goes, and that's where Pepe's paper comes in. Pepe's data compiled in the paper contained body mass, body length, and maximum relative running speed for each animal, where the relative running speed was defined as body lengths per second. In order to keep the trends relevant for running (to quote part of his paper), "Species with highly specialised habits and limb morphologies, such as arboreal and fully fossorial species, were excluded from the analysis."

One of his major results was to show that maximum relative running speed decreases with increased body mass, and to comue up with a trend describing the relationship.

Fig. 1. Maximum relative running speed of 142 species of mammals. Dashed line represents the LOWESS non-parametric smoothed regression fit (sampling proportion=0.6). Dotted line indicates the point of slope change (k=30 kg) in the one point-change regression model. Solid lines represents the fit under the ordinary least-squares method (OLS) for small and large mammals. Filled squares, Rodentia; open squares, Primata; filled diamonds, Proboscidae; open diamonds, Marsupialia; filled triangles, Carnivora; open triangles, Artiodactyla; filled circles, Perissodactyla; open circles, Lagomorpha.

Since his data was "maximum" running speed, it was exactly what I was looking for to compare human sprinting abilities with other animals in general, and not just comparing us to the fastest like documentaries commonly do. I took his data and input it into Excel, so I could do my own playing around with it. First was to reproduce his graph, to make sure I'd input the data properly. On my version of the graph, I've highlighted humans, so you can see where we fall. I've also highlighted the most famous of all sprinters, the cheetah.


Next, I took his figures for body length and maximum relative running speed, and calculated a maximum actual running speed. For this graph, I converted speed to mph, and body weight to pounds (since I'm an engineer, not a scientist, and these units make the data easier for me to grasp). Once again, I've highlighted humans and cheetahs.


So, after looking at the data this way, while humans are definitely at the low end of the range, we're certainly not outliers in the data. We fit in comfortably compared to other animals, actually sprinting faster than a few of the animals in our weight class. Taking into account our endurance running capabilities, I'd say that humans really aren't too bad of runners, after all.

I guess next it's time to try to compare us to the other animals in other ways, such as our senses, or maybe our strength. If it takes me as long to research another one as my blog entries typically take, expect another update in a few years.

Tuesday, July 4, 2006

Comment Registration

Okay, it's come to this. Users now have to register through Type Key to comment on this blog. I didn't want to do it, because I wasn't getting many legitimate comments as it was, and I didn't want to make it any more difficult for people to leave feedback, but the spam was just getting to be too much. But at least Type Key is pretty painless. It's free, it gives you the option to stay signed in for up to two weeks so you won't be having to type in your user name and password very often, and it only requires a one time sign up for any of the thousands of blogs that use it. In other words, if you've already signed up for Type Key to comment on a popular site like Pharyngula, that same account will work to allow you to comment on my not so popular site. Sorry for the inconvenience.

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