One of the greatest things about Astrobiology is how expansive it is - it literally includes everything "in heaven and in the earth, and under the earth; things which have been, things which are, [and] things which must shortly come to pass" (DC 88:79). Today's entry is about the topic of evolution, which is not my main field of study, but is something that falls under the purview of astrobiology.
Today I came across this article from the science news site Science Daily, which by the way, is a site I really like for news from all fields of science. The article is on animal evolution, and specifically about why we have four limbs. It's been known for quite some time that all mammals. birds, reptiles and amphibians are tetrapods, meaning they have four limbs. The limbs could be fins, wings or arms and legs (or even tiny stubs that you'd never notice), but they're all related to each other. But the reason for why all these animals have four lime is still an unsolved problem in biology.
Very early in the development of all the embryos the group looked at, the embryos form into 3 distinct layers, known as germ layers. Each of the three germ layers has a specific purpose - the ectoderm (outside layer) generally forms the skin and nervous system, the endoderm (inside layer) forms the digestive tract and many other essential organs, and the mesoderm (middle layer) generally forms muscle, tissue, bone and other parts of the body.
Very early on in an embryo's development the mesoderm splits into two separate layers. The hypothesis presented in this paper is that pairs of limbs can only form where these mesoderm layers interact with the ectoderm. Between these points, they propose that limbs simply can't form because the gut is developing.
To be completely honest, reading about this left me with a lot more questions than answers, but parts of it make sense. The gut is really the most important part of any organism. Without the ability to have energy sources come in and be turned into something the body can use, the organism dies. I could imagine that growing an extra leg or two right next to the developing digestive system might interfere with survival. That being said, I'm still not sure why limbs can only form there, or how exactly this process happens.
The spiritual conclusion I came to while reading this is that we really are created in God's image. There's something innate about the way we look that isn't random. It could be that the laws of physics simply don't allow anything else. I don't know though, that's pure speculation. What I do know is that God created this Earth and everything on it with a plan. Call it intelligent design if you'd like, but I know that as we keep learning about how evolution worked that more things like this will be discovered, and we'll see God's hand in the entire process.
Today I came across this article from the science news site Science Daily, which by the way, is a site I really like for news from all fields of science. The article is on animal evolution, and specifically about why we have four limbs. It's been known for quite some time that all mammals. birds, reptiles and amphibians are tetrapods, meaning they have four limbs. The limbs could be fins, wings or arms and legs (or even tiny stubs that you'd never notice), but they're all related to each other. But the reason for why all these animals have four lime is still an unsolved problem in biology.
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| The researchers were studying animals hatchlings and embryos and comparing physiological features. (From Science Daily) |
Very early in the development of all the embryos the group looked at, the embryos form into 3 distinct layers, known as germ layers. Each of the three germ layers has a specific purpose - the ectoderm (outside layer) generally forms the skin and nervous system, the endoderm (inside layer) forms the digestive tract and many other essential organs, and the mesoderm (middle layer) generally forms muscle, tissue, bone and other parts of the body.
Very early on in an embryo's development the mesoderm splits into two separate layers. The hypothesis presented in this paper is that pairs of limbs can only form where these mesoderm layers interact with the ectoderm. Between these points, they propose that limbs simply can't form because the gut is developing.
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| Sorry, no centaurs allowed in this universe apparently. |
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| But I suppose a god may be able to muster a one or two (dozen) extra arms |
To be completely honest, reading about this left me with a lot more questions than answers, but parts of it make sense. The gut is really the most important part of any organism. Without the ability to have energy sources come in and be turned into something the body can use, the organism dies. I could imagine that growing an extra leg or two right next to the developing digestive system might interfere with survival. That being said, I'm still not sure why limbs can only form there, or how exactly this process happens.
The spiritual conclusion I came to while reading this is that we really are created in God's image. There's something innate about the way we look that isn't random. It could be that the laws of physics simply don't allow anything else. I don't know though, that's pure speculation. What I do know is that God created this Earth and everything on it with a plan. Call it intelligent design if you'd like, but I know that as we keep learning about how evolution worked that more things like this will be discovered, and we'll see God's hand in the entire process.
The full paper is available for free here. The title is "The lateral mesodermal divide: an epigenetic model of the origin of paired fins," Evolution & Development, 2014 by Laura Nuño de la Rosa, Gerd B. Müller, and Brian D. Metscher from the University of Vienna.
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