Tag Archives: origin of life

Better living through chemistry

3.20-3.04 billion years ago

Chemistry plays a big role once Earth forms. Different mineral species appear, with different chemical compositions. Magnesium-heavy olivine sinks to the lower mantle of the Earth. Aluminum-rich feldspars float to the top.

Chemistry is an example of what William Abler calls “the particulate principle of self-diversifying systems,” what you get when a collection of discrete units (atoms) can combine according to definite rules to create larger units (molecules) whose properties aren’t just intermediate between the constituents. Paint is not an example. Red paint plus white paint is just pink paint. But atoms and molecules are: two moles of hydrogen gas plus one mole of oxygen gas, compounded, make something very different, one mole of liquid water.

A lot of important chemical principles are summed up in the periodic table.

periodictable copy

On the far right are atoms that have their electron shells filled, and don’t feel like combining with anyone. Most, but not all the way, to the right are atoms with almost all their shells filled, just looking for an extra electron or two. (Think oxygen, O, with slots for two extra electrons). On the left are atoms with a few extra electrons they can share. (Think hydrogen, H, each atom with an extra electron it’s willing to share with, say, oxygen.) In the middle are atoms that could go either way: polymorphously perverse carbon, C, with four slots to fill and four electrons to share, and metals, that like to pool their electrons in a big cloud, and conduct electricity and heat easily. (Think of Earth’s core of molten iron, Fe, a big electric dynamo.)

Another example of “the particulate principle of self-diversifying systems” is human language. Consider speech sounds, for example. You’ve got small discrete units (phonemes, the sounds we write bpskchsh, and so on) that can combine according to rules to give syllables. Some syllables are possible, according to the rules of English, others not. Star and spikythole and plast, are possible English words, tsar and psyche are not (at least if you pronounce all the consonants, the way Russians or Greeks do), nor tlaps nor bratz (if you actually try to pronounce the z). Thirty years ago appblog, and twerk were not words in the English language, but they were possible words, according to English sound laws.

You can make a periodic table of consonants.

phonemes

Across the top are the different places in the vocal tract where you block the flow of air. Along the left side are different ways of blocking the flow (stopping it completely –t-, letting it leak out –s-, etc.) The table can explain why, for example, we use in for intangible and indelicate, but switch to im for impossible and imbalance. (The table contains sounds we don’t use in English, and uses a special set of signs, the International Phonetic Alphabet, which assigns one letter per phoneme.) This is why a book title like The Atoms of Language makes sense (a good book by the way).

So sometimes the universe gets more complex because already existing stuff organizes itself into complex new patterns  – clumps and swirls and stripes. But sometimes the universe gets more complex because brand new kinds of stuff appear, because a new particulate system comes online: elementary particles combine to make atoms, atoms combine to make molecules, or one set of systems (nucleotides to make genes, amino acids to make proteins) combines to make life, or another set of systems (phonemes to make words, words to make phrases and sentences) combines to make language.

Advertisements

My name is LUCA. I live on the ocean floor.

How life began on Earth is still not well understood. The “RNA world” is one popular theory. In modern organisms, nucleic acids, DNA and RNA, store and transfer information, but proteins do the actual work of catalyzing chemical reactions. But RNA can act as a catalyst, so maybe the first replicating systems involved RNA catalyzing its own replication. However, RNA doesn’t spontaneously form very easily, so it’s not clear how the RNA world would have gotten started. Borate minerals might help but it’s not clear they were around that early.

Another possibility that’s gotten some attention lately involves droplets that grow and divide, instead of just merging into bigger drops.

A different approach to the topic is to work backward from living organisms, to reconstruct the biochemistry of LUCA, the Last Universal Common Ancestor (not quite the same as the first living thing). Recent research on these lines implies that LUCA was a heat-loving microbe that relied on hydrogen as its energy source, suggesting an undersea volcano as a habitat.

However the first organisms got established on Earth, it happened very quickly. Just about as soon as the planet could support life we find chemical evidence for it, from Isua, Greenland (but no fossils yet). This suggests that the origin of life is pretty easy (unless we want to go with panspermia). Mars may have been a more habitable place early in its history, and perhaps Mars exploration will one day solve the mystery of the origin of life in our Solar System.

Where is everybody? Maybe we’re (some of) the first.

A followup to yesterday’s post on the Fermi Paradox, some reasons the Universe could have been less suitable for the evolution of complex life until recently, making us one of the first intelligent species to evolve.

1) Metallicity. Chemical elements heavier than helium are formed inside stars, after the Big Bang. Elements heavier than iron are formed in exploding supernovas. These elements have been building up over time. Maybe they had to reach a threshold abundance to make complex life possible.

On its own, it’s not clear this would have prevented intelligent life from arising long ago. The Sun has a high “metallicity” (concentration of heavy elements), but there are stars in the Milky Way older than the Sun with higher metallicities. But metallicity could combine with GRBs (below): toward the center of the galaxy there are more heavy elements but also more GRBs.

2) Gamma Ray Bursts (GRBs). GRBs are bursts of gamma rays (high frequency radiation) lasting from milliseconds to minutes, like GRB 080319B. (Check out tweets for January 11.) They are probably supernovas or even larger explosions with one pole of the exploding star pointed at the Earth. A major GRB could irradiate one side of the planet, and also affect the other side by destroying the ozone layer, causing mass extinctions. GRBs may have swept the Milky Way frequently in the past. The good news is they’re probably getting less frequent. This could be the first time in the history of the Milky Way that enough time has passed without a major GRB for intelligent life to evolve. If true, we should think about how to protect ourselves from the next one – lots of sunblock recommended.

If GRBs are such a threat, we might expect to find evidence that they have caused mass extinctions in the past (not wiping out all life obviously). For more on this, check out upcoming blog posts and tweets for the end-Ordovician, March 3.

3) Panspermia (life from elsewhere). Pretty much as soon as Earth could support life, we see evidence of single-celled organisms. Then life evolves slowly for a long time. The usual story about this is that the origin of life is easy, and it happens as soon as possible. But there is another possibility (illustrated below). It may be that the transition from simple replicating chemical systems to bacteria with genomes of tens of thousands of DNA base pairs is a slow process that happened over many billions of years somewhere off Earth. Then newly forming planets in the nebula that gave rise to Earth were “infected” by this source, by meteorites carrying early cells. (It would have been easier for meteorites to carry life from star system to star system when the Earth was first formed than it would be today.) Back when our hypothetical “Urth” was forming, a billion years before Earth, there might not have been any planets with cellular life on them as potential sources of life-bearing meteorites.

Untitled

Where is everybody?

Today, January 16, covers the period 5.62 to 5.31 billion years ago in Logarithmic History, beginning a billion years before the origin of our solar system. Back then, stars were forming at a fast clip in the Milky Way and other spiral galaxies. So let’s suppose… Suppose one of those older stars resembled the Sun, and had a planet like Earth orbiting around it – call it Urth. And suppose life originated on Urth more or less as on Earth and followed more or less the same evolutionary path. With this head start, intelligent life could have evolved a billion years ago, and today there could be intelligent Urthians (or their robot descendants) a billion years ahead of us.

There’s an urban legend that says that Einstein called compound interest the strongest force in the universe. Einstein didn’t actually quite say this, but it’s not a crazy thing to say. For example, consider how compound interest works, backward, on our Logarithmic History calendar. December 30 covers a period 5.46% longer than December 31, December 29 is 11.1% longer (because 1.0546 * 1.0546 = 1.112), and so on. At this rate of compounding we wind up with January 1 covering 754 million years. The same math implies that if we invested 1 dollar at 5.46% interest, compounded annually, then after 364 years we’d have 754 million dollars.

With even the slightest compound rate of increase, a billion year old Elder Race would have plenty of time to fill up a galaxy, and undertake huge projects like dismantling planets to capture more of their suns’ energy. Which raises the question, posed by Enrico Fermi in 1950: “Where is everybody?” There are more than 100 billion stars in our galaxies, more than 100 billion galaxies in the visible universe (actually, according to recent estimates, the number may be more than  1 trillion). If there are huge numbers of billion year old Elder Races around, why hasn’t at least one of them taken the exponential road and made themselves conspicuous?

There’s a large literature on the Fermi paradox. Here I consider just one sort of explanation. Maybe we’re one of the first intelligent species to evolve because the universe was somehow less suitable for the evolution of complex life before now. (To be continued).

Better living through chemistry

January 27. 3.29 – 3.04 Bya (billion years ago)

Chemistry plays a big role once Earth forms. Different mineral species appear, with different chemical compositions. Magnesium-heavy olivine sinks to the lower mantle of the Earth. Aluminum-rich feldspars float to the top.

Chemistry is an example of what William Abler calls “the particulate principle of self-diversifying systems,” what you get when a collection of discrete units (atoms) can combine according to definite rules to create larger units (molecules) whose properties aren’t just intermediate between the constituents. Paint is not an example. Red paint plus white paint is just pink paint. But atoms and molecules are: two moles of hydrogen gas plus one mole of oxygen gas, compounded, make something very different, one mole of liquid water.

A lot of important chemical principles are summed up in the periodic table.

periodictable copy

On the far right are atoms that have their electron shells filled, and don’t feel like combining with anyone. Most, but not all the way, to the right are atoms with almost all their shells filled, just looking for an extra electron or two. (Think oxygen, O, with slots for two extra electrons). On the left are atoms with a few extra electrons they can share. (Think hydrogen, H, each atom with an extra electron it’s willing to share with, say, oxygen.) In the middle are atoms that could go either way, including metals that like to pool their electrons in a big cloud, and conduct electricity and heat easily. (Think of Earth’s core of molten iron, Fe, a big electric dynamo.)

Another example of “the particulate principle of self-diversifying systems” is human language. Consider speech sounds, for example. You’ve got small discrete units (phonemes, the sounds we write b, p, s, k, ch, sh, and so on) that can combine according to rules to give syllables. Some syllables are possible, according to the rules of English, others not. Star and spiky, thole and plast, are possible English words, tsar and psyche are not (at least if you pronounce all the consonants, the way Russians or Greeks do), nor tlaps nor bratz (if you actually try to pronounce the z). Thirty years ago app, blog, and twerk were not words in the English language, but they were possible words, according to English sound laws.

You can make a periodic table of consonants.

phonemes

Across the top are the different places in the vocal tract where you block the flow of air. Along the left side are different ways of blocking the flow (stopping it completely –t-, letting it leak out –s-, etc.) The table can explain why, for example, we use in for intangible and indelicate, but switch to im for impossible and imbalance. (The table contains sounds we don’t use in English, and uses a special alphabet with one letter per phoneme.) This is why a book title like The Atoms of Language makes sense (a good book by the way).

A lot of the major leaps in complexity in the history of the universe (the ones that go beyond just already existing stuff organizing itself in clumps and swirls and stripes) happen when brand new kinds of stuff appears because a new particulate system comes online: when elementary particles combine to make atoms, atoms combine to make molecules, and multiple systems (nucleotides to make genes, amino acids to make proteins) combine to make life.

Where is everybody? Maybe we’re (some of) the first.

A followup to yesterday’s post on the Fermi Paradox, some reasons the Universe could have been less suitable for the evolution of complex life until recently, making us one of the first intelligent species to evolve.

1) Metallicity. Chemical elements heavier than helium are formed inside stars, after the Big Bang. Elements heavier than iron are formed in exploding supernovas. These elements have been building up over time. Maybe they had to reach a threshold abundance to make complex life possible.

On its own, it’s not clear this would have prevented intelligent life from arising long ago. The Sun has a high “metallicity” (concentration of heavy elements), but there are stars in the Milky Way older than the Sun with higher metallicities. But metallicity could combine with GRBs (below): toward the center of the galaxy there are more heavy elements but also more GRBs.

2) Gamma Ray Bursts (GRBs). GRBs are bursts of gamma rays (high frequency radiation) lasting from milliseconds to minutes, like GRB 080319B. (Check out tweets for January 11.) They are probably supernovas or even larger explosions with one pole of the exploding star pointed at the Earth. A major GRB could irradiate one side of the planet, and also affect the other side by destroying the ozone layer, causing mass extinctions. GRBs may have swept the Milky Way frequently in the past. The good news is they’re probably getting less frequent. This could be the first time in the history of the Milky Way that enough time has passed without a major GRB for intelligent life to evolve. If true, we should think about how to protect ourselves from the next one – lots of sunblock recommended.

If GRBs are such a threat, we might expect to find evidence that they have caused mass extinctions in the past (not wiping out all life obviously). For more on this, check out upcoming blog posts and tweets for the end-Ordovician, March 2.

3) Panspermia (life from elsewhere). Pretty much as soon as Earth could support life, we see evidence of single-celled organisms. Then life evolves slowly for a long time. The usual story about this is that the origin of life is easy, and it happens as soon as possible. But there is another possibility (illustrated below). It may be that the transition from simple replicating chemical systems to bacteria with genomes of tens of thousands of DNA base pairs is a slow process that happened over many billions of years somewhere off Earth. Then newly forming planets in the nebula that gave rise to Earth were “infected” by this source, by meteorites carrying early cells. (It would have been easier for meteorites to carry life from star system to star system when the Earth was first formed than it would be today.) Back when our hypothetical “Urth” was forming, a billion years before Earth, there might not have been any planets with cellular life on them as potential sources of life-bearing meteorites.

Untitled

Where is everybody?

Today, January 16, covers the period 5.96 to 5.63 billion years ago in Logarithmic History, just over a billion years before the origin of our solar system. Back then, stars were forming at a fast clip in the Milky Way and other spiral galaxies. So let’s suppose… Suppose one of those older stars resembled the Sun, and had a planet like Earth orbiting around it – call it Urth. And suppose life originated on Urth more or less as on Earth and followed more or less the same evolutionary path. With this head start, intelligent life could have evolved a billion years ago, and today there could be intelligent Urthians (or their robot descendants) a billion years ahead of us.

There’s an urban legend that says that Einstein called compound interest the strongest force in the universe. Einstein didn’t actually quite say this, but it’s not a crazy thing to say. For example, consider how compound interest works, backward, on our Logarithmic History calendar. December 30 covers a period 5.44% longer than December 31, December 29 is 11.1% longer (because 1.0544 * 1.0544 = 1.111), and so on. At this rate of compounding we wind up with January 1 covering 751 million years. The same math implies that if we invested 1 dollar at 5.44% interest, compounded annually, then after 365 years we’d have 751 million dollars.

With even the slightest compound rate of increase, a billion year old Elder Race would have plenty of time to fill up a galaxy, and undertake huge projects like dismantling planets to capture more of their suns’ energy. Which raises the question, asked by Enrico Fermi in 1950: “Where is everybody?” There are more than 100 billion stars in our galaxies, more than 100 billion galaxies in the visible universe. If there are huge numbers of billion year old Elder Races around, why hasn’t at least one of them taken the exponential road and made themselves conspicuous?

There’s a large literature on the Fermi paradox. Here I consider just one sort of explanation. Maybe we’re one of the first intelligent species to evolve because the universe was somehow less suitable for the evolution of complex life before now. (To be continued).