For those GEITP-ers interested further in this topic of “the Origin of Life,” D.Lancet et al. [see attached] are advocating a systems protobiology view, whereby the first replicators are proposed to be assemblies of spontaneously accreting, heterogeneous and mostly non-canonical (unrelated, not conforming) amphiphiles [molecules that are both water-loving (hydrophilic, polar) and fat-loving (lipophilic)]. This approach is supported by rigorous chemical kinetics simulations of the Graded Autocatalysis Replication Domain (GARD) model — based on the reasonable notion that replication or reproduction of compositional information predated that of sequence information.
Authors [attached pdf at right] show a preliminary new version of their model, metabolic GARD (M-GARD), in which lipid covalent modifications are carried out by non-enzymatic lipid catalysts — themselves compositionally reproduced. M-GARD fills the gap of the lack of true metabolism in basic GARD, and is reinforced by a published experimental instance of a lipid-based mutually catalytic network. GARD analysis in a whole-planet context offers the potential for estimating probability of life’s emergence. The concepts presented in this review enhance the validity of autocatalytic sets as a bona fide early-evolution scenario.
Sent: Tuesday, February 05, 2019 4:03 PM
I am glad to see this Origin of Life item among your emails. I am not sure I ever told you that in the last 20-some years I have worked quite extensively on this topic. Just to share with you this relatively rcent interst, I am attaching the 2018 reprint, our latest on the topic. I would be delighted to share with you in more detail my rather unorthodox model of how life arose.
Warm regards, xx
Dept. Molecular Genetics
Weizmann Institute of Science
Herzl 234, Rehovot 7610010, Israel
From: Nebert, Daniel (nebertdw)
Sent: Tuesday, February 05, 2019 3:33 PM
Subject: Here is a new opinion as to how life on our planet might have emerged
As these GEITP pages have previously detailed, Earth formed ~4.53 billion years ago (approximately one-third of the 13.8-billion-year age of the universe); this happened by accretion (gravitational attraction of gaseous particles) of material from solar nebula (Solar System cloud). Volcanic eruptions, followed by contributions from oceans, most likely created the primordial atmosphere — which contained barely any diatomic O2. Early in Earth’s existence, a major collision ~4.51 billion years ago (with a planet-sized body named Theia) is believed to have formed the moon. The Hadean eon represents the era before reliable (fossil) evidence of life (i.e. beginning with Earth’s formation and ending ~4.0 billion years ago).
A new scenario [see attached editorial] suggests that ~4.47 billion years ago — a moon-size object might have sideswiped Earth and exploded into an orbiting cloud of molten iron and other metals; dense elements (e.g. iron, gold, platinum, and palladium), should have sunk to the planet’s core, whereas silicon and other light elements would have floated nearer the surface. Yet, those metals remain plentiful near the planet’s
surface — at levels thousands of times more abundant than they should be.
The metallic hailstorm likely continued for centuries, ripping oxygen atoms from water molecules and binding to iron atoms, creating vast rust-colored deposits of iron oxide across Earth’s surface. After things cooled down, simple organic molecules began to form under the blanket of hydrogen as a catalyst. Those molecules are proposed to have linked up eventually, to form RNA starting ~4.35 billion years ago, the molecular player long credited as essential for the beginning of life and existing before DNA. In other words, the stage for life’s emergence was set, almost as soon as our planet was born. Because of altered ratios of carbon isotopes in zircon, ~4.1 billion years ago, these data suggest hints of the earliest of life forms [see Figure in attached editorial].
This scenario fascinated participants at an October 2018 Origins of Life Workshop in Atlanta — where geologists, planetary scientists, chemists, and biologists compared notes on the latest thinking as to how life might have started on Earth. No rocks or other direct evidence remain from the hypothetical cataclysm; however, its starring role is inferred, because “it would solve a bevy of mysteries.” The metal-laden rain would account for the distribution of metals across our planet’s surface today. The hydrogen atmosphere would have favored emergence of the simple organic molecules, which later formed more complex molecules such as RNA. And the planetary collision would move back the likely birthdate for RNA, and possibly life’s emergence, by hundreds of millions of years.
This hypothesis aligns itself better with recent geological evidence, suggesting an early emergence of life. Many in the “origins-of-life” field now see a consistent narrative beginning to take shape — as far as describing how and when life began on Earth.
Science 11 Jan 2019; 363: 116–119 [Opinion]