How Did Life Begin?

[Music] what is life where did we come from water is h2o two atoms of hydrogen and one of oxygen pulled together by covalent bonds the air we breathe is a mix of countless particles along with dust and water vapor then what is it that makes up life what are the ingredients of our fundamental essence and what is it that separated us nearly four billion years ago and continues to separate us today from everything else oh no doubt many individuals in the ancient world concern themselves with these great questions it was the Greeks from around the seventh century BC onwards who turned it into a viable career path many philosophers of the Greek world the like of Epicurus Lucretius and Plato be occupied themselves with where life came from the overwhelming conclusion was that life baguettes life but what of the first life what began that in the fourth century BC Aristotle concluded that living things arise spontaneously from nonliving matter as long as that matter contained in nuuma or vital heat worms he surmised arose spontaneously from decaying manure insects sprang forth from the morning dew and eels Servet newborn from nothing more than a wet booze and rotting seaweed remarkable as this may seem to us now Aristotle's ideas of spontaneous generation dominated thinking on the origin of life for nearly 2,000 years the scientists that followed in his footsteps devising ever more complex recipes for higher forms of life like early 17th century Dutch scientist jean-baptiste van Helmont who reasoned that a dirty shirt left in a bin with wheat germ for 21 days but spontaneously generate live mice over time though the recipes for spontaneous life lost favor science advanced and explanations were found for the seemingly miraculous appearance of animals in old abandoned heaps of dirt but for the smaller enigmatic creatures bacteria and weird single-celled amoebas spontaneous generation proved hard to disprove finally in the 19th century French biologist Louis Pasteur devised an experiment to exclude any outside influence from a flask full of inanimate matter a vacuum when the flask remains sterile the concept of spontaneous generation was proved to be false matter alone could not make life after all to this day no laboratory has been able to pull life from its absence Frankenstein remains a fiction life and only life has continued to beget life and yet we know today that the earth formed more than four billion years ago without life no living thing could have survived the convulsions of the Hadean Eon but here we are today on an earth brimming with overflowing with living beings of every imaginable form and function from rainforest to desert from the highest peaks to the deepest ocean depths life thrives so it is abundantly clear at some point between three to four billion years ago matter did make life the final act of spontaneous generation in history the origin of life on earth the questions that remain a how and from what [Music] the first life on earth must have been the simplest possible life form no mice could have sprouted spontaneously into being on a late Hadean Eon earth in order to decipher where life came from we must first consider what exactly life is at its most basic level a monumental task requiring all the efforts of modern scientific technique in most education systems humans learn to define living things by what they do animals plants and fungi taking steps to maintain themselves grow and reproduce but this isn't the full story living creatures might do these things but they're not the only ones by this definition we would class some crystals as being alive or computer viruses algorithms even today this is not the standard definition for the origin of organic life on Earth instead we need to zoom in to the microscopic level to see what living things are made of the simplest forms of life today bacteria have two basic ingredients a self-replicating molecule like DNA that contains the instructions for making another one of itself and a self-contained metabolism that provides the machinery to do the living and the replicating defined like this we capture the essence of every living thing on planet Earth everything is made up of cells like the bacterial cell which at their core have a self-replicating molecule and a self-sustaining metabolism this definition gives viruses a place on the road to life - even if they don't quite qualify these tiny structures have a self-replicating molecule within them just like every other living thing but they lack the machinery to do anything with that molecule instead they must hijack other organisms to borrow the organic factories that will allow them to reproduce some scientists would class them as alive others would not some even think that they may be a piece in the puzzle of life's origins a kind of halfway point between living and dead so a self-replicating molecule and a metabolism were the two inventions needed for the very first life-forms but they're not simple inventions our DNA is a giant complex macromolecule a long double strand made up of millions of smaller simpler molecules they themselves built from atoms of carbon oxygen hydrogen nitrogen and many more the modern metabolism built around this monster molecule is a complex organic factory to each part finely tuned to a particular function and interdependent on everything else to keep running of course life couldn't start out with something so elaborate its beginnings were necessarily much simpler using basic building blocks that already existed on the early earth or that were made for the first time inside its young oceans so to find the true beginning we have to go back and examine the chemical composition of this young world of all the possible elements in the universe 94 occur naturally on our planet every element is characterized by its behavior its affinity for other elements and the energy needed to make or break connections some don't react at all others like silicon react slowly needing huge amounts of energy to restructure its molecules silicon is abundant on the earth but not a good candidate for shifting reactive biological life carbon is a stronger choice the fourth most common element in the solar system it can easily form strong bonds with other carbon atoms as well as with other abundant elements oxygen hydrogen nitrogen all life on Earth is based on this cosmopolitan element combined with oxygen and hydrogen in what are now called organic molecules in fact the Hadean earth was a melting pot of organic opportunity sugars which were destined to become the backbone to our genetic molecules and the fuel for our cellular factories were made with cosmic chemistry and formed in the star forming regions of the Milky Way they floated freely in the early ocean nuclear bases to simple nitrogen containing compounds that when combined form the basis for information storage in our self-replicating molecules the molecular language of life's instruction manual a repeating pattern of four different nuclear bases encodes all the instructions for how to stay alive grow and reproduce on the early earth they could have been a spontaneous product of primordial chemistry finally amino acids also ubiquitous to all life on Earth they are the building blocks of proteins from which almost all cellular machinery is shaped [Music] to prove this back in the 1950s to American scientists Stanley Miller and Harold Urey designed a now famous experiment to try and create these amino acids from what they believed the composition of the early atmosphere to be they started with a mixture of water methane ammonia and hydrogen and ran an electric spark through that mixture on the early earth the same conditions could have been created by a lightning bolt spearing down from the thunder clouds that capped the first mountains the result was the creation of entirely new chemicals including several of the amino acid building blocks that all life on Earth uses they proved that organic molecules could in fact be made from inorganic matter so the building blocks existed as a kind of organic soup in Earth's early oceans but this alone is not life the molecules must come together in a very specific way to form self-replicating molecules and protein machinery the key to life and therein lies the paradox today almost all living things use DNA as their self-replicating molecule the patterns of nuclear bases in the molecule encode all the instructions for growing and reproducing and making proteins but of course 20v do these things it needs protein machinery to read the instructions interpret them and make new components it needs the hands to do the work so proteins are needed to read and reproduce the DNA but the DNA instructions are needed to make the proteins in the first place it's the ultimate conundrum the original chicken and egg what came first the proteins or DNA we are back at the beginning our primary problem the loop continues life baguettes life yet again yet the true answer is probably neither the DNA or the proteins scientists today think that another molecule bridge the gap the true prototype for the complex machinery that powers our existence the true beginning of life on earth beneath the churning chaos of Hadean Earth's deep oceans potentially for the first time a molecule successfully replicates itself [Music] our n a as it is known is a self-replicating single stranded molecule similar to but simpler than DNA it can replicate but it can also not itself up into 3d structures very similar to the protein machinery used in living things today scientists believe RNA could have been a catch-all molecule that performed all the functions of early metabolism and replication the result would have been what scientists call the RNA world where all of biology is made up of this single-stranded nuclear base pattern in the prebiotic soup random combinations of sugars and nuclear bases come together and are joined spontaneously by chemical reactions some break apart again but some stay stuck and continue to grow into long strands one nuclear base after another sometimes the Strand effects its own structure coiling or folding back in on itself in this way a kind of pre life natural selection takes hold to select the kinds of molecules that are structurally stable and mechanically useful the stable strands can act as templates for replication for making another identical to itself that the bunched up strands acting as rudimentary machines to help that replication along a whole ecosystem of different RNA molecules emerges proliferating and diversifying more stable strands replicating more successfully floating freely within the primordial soup [Music] but this too is not yet life the RNA ecosystem alone is a fluke of chemistry not a self-sustaining organism any chemical imbalances in the primordial oceans could have collapsed and destroyed the entire RNA world even the smallest puddle on the primordial earth is a big place for a fragile strand of RNA the chemicals needed for metabolic chemical reactions being impossibly diluted the chances of them running into each other are vanishingly small promising reactions all the while being disrupted by other chemicals floating around in the water so for metabolism to really get going the reactions needed a box to happen in separated from the outside environment where chemicals were concentrated and where the RNA could help direct the composition within all living things rely on these compartments these boxes some make do with just one others have trillions [Music] just like the machinery within the earliest cells probably looked very different to today modern cells have infinite variety and complexity but the earliest cells would have been much simpler but there's a good chance they were made of similar material called fatty acids these two would have formed spontaneously from chemical reactions in the prebiotic soup but it's their interaction with the surrounding water that makes them special fatty acids and the molecular relatives have a two part structure part is attracted to water while the other part is repelled by it so what does a fatty acid do when it finds itself immersed in water it cannot tear itself apart to satisfy both halves of its bi-polar nature instead it seeks solace in groups spontaneously self-organizing into spherical structures that shield the water heating portions while allowing the water loving parts to bathe in the soothing Wash fatty acids may not have been the most abundant molecule on the early Earth but their spontaneous self-organization makes them promising candidates for the earliest protocells larger spheres could easily have contained strands of replicating RNA the environment inside isolated and protected chemical reactions can happen in this new concentrated internal environment they can be influenced and directed by the RNA strands and the changes inside influence the strands themselves the first tentative metabolisms arise natural selection of chemical stability meaning that only those concoctions that favor self-preservation and perpetuation can stick around from starborn atoms and molecules concentrated on the young Earth's volatile surface giant macromolecules formed found ways to reproduce and pass their success on to new generations with survival the sole purpose in proving and warping along the way just this one time life arose spontaneously matter begat life allowing life to beget life for another three and a half billion years and counting next time we follow life back to its last Universal common ancestor and find out where on earth these first tentative steps into biology took place we'll explore the controversy around the very first fossils and consider the possibility that life itself may have been delivered from space you've been watching the entire history of the earth don't forget to Like subscribe and share and let us know in the comments what you'd like to see covered in the future thanks for watching and we'll see you next time

Channel: History of the Earth

Views: 502,444

Keywords: Life, First Life, Science, History, Beginning of Life, Genesis, Cells, RNA, DNA, How life started, How did life start?, Life on earth, 4 billion years ago, earth, documentary, earth science, geology

Id: WZCeOUSYb4g

Length: 21min 30sec (1290 seconds)

Published: Sat Jul 04 2020

Reddit Comments

[u/JediMasterZao]

That is an exceedingly good science narrator!