From: jimruttshow8596
The origin of life is a field of study that explores the transition from the abiotic (non-living) world to the biotic (living) world [07:22:15]. This complex process involves understanding how organized chemical systems emerged and became self-sustaining [11:33:07].
Key Researchers and Concepts
Eric Smith, a statistical physicist, is a prominent researcher at the Earth Life Science Institute in Tokyo and a faculty member at Georgia Tech, with external faculty status at the Santa Fe Institute (SFI) [00:33:14]. His work in the origins of life field began through an interest in dynamical phase transitions as a way to understand how biology works [07:58:39].
He collaborated extensively with Harold Morowitz, a biophysicist and physiologist, leading to their co-authorship of “The Origin and Nature of Life on Earth: The Emergence of the Fourth Geosphere” [01:27:14], [08:18:24].
Metabolism First vs. Control First
The field has seen differing perspectives on the initial emergence of life:
- Control First (RNA World Hypothesis): This view, influenced by Francis Crick’s central dogma, posited that control flows from DNA to RNA to proteins, and attempted to map this flow directly to the beginning of life [10:06:05]. It placed a “heavy burden” on RNA molecules to serve as both genotype and phenotype [10:29:06]. Chemically, this is considered very difficult due to RNA’s complexity [10:36:20].
- Metabolism First: This perspective argues that deep small-molecule biochemistry laws were inherited from regularities in geochemistry that existed before the biosphere formed [11:01:24]. It suggests that life’s emergence was not a single event but a cascade of increasingly organized states of geochemistry, setting a template for biochemistry [11:25:35].
The Fourth Geosphere
Harold Morowitz’s key insight was to view the biosphere as a “fourth geosphere” [13:52:08]. Traditionally, Earth has three main geospheres identified by Vladimir Vernadsky:
- Lithosphere: The solid core of the planet, defined by solid-state chemistry and physics [13:10:02].
- Hydrosphere: The liquid ocean, characterized by water chemistry [13:18:13].
- Atmosphere: The gas phase, coupled to stellar irradiance, with distinct chemistry and state of matter [13:27:07].
Morowitz argued that the biosphere is a new, dynamically defined state of matter with its own distinctive rules, more integrated by its internal processes than by its exchanges with other planetary components [13:58:39]. This means life’s origin is “something that happens to a planet” rather than just on it [15:10:36].
Hypotheses on the Emergence of Life
There are various hypotheses regarding where and how life might have originated:
- Subsurface Water Alteration Zones / Deep Rock Theories: These zones are considered very good places for planetary chemistry due to conditions favorable for electron transfer potentials and catalytic environments [14:37:37].
- Black Smoker Theories: This refers to hydrothermal vents on the seafloor, which are also considered potential sites.
- Spreading Centers: Eric Smith suggests that the best candidates for the organization of organic chemistry are the spreading centers underneath ocean basins, where new crust is formed [18:31:07]. This environment offers a “controlled” and “mild” chemistry, low in energy, which is much closer to biochemistry than other extreme conditions [18:54:19].
Energetic and Chemical Drivers
The Earth itself is considered a “battery” [17:33:04]. An electron flow occurs from the deep bulk of the Earth into the atmosphere due to processes like water splitting by solar radiation [18:07:05]. This electron flow, particularly at spreading centers, provides the energy for life’s emergence [18:27:26].
Low-energy chemistry, prevalent in these environments, necessitates catalysts for reactions to occur [19:10:19]. Core biochemical pathways, such as the citric acid cycle, are central to carbon fixation and the synthesis of all other biochemical components, acting as a “foundation” for biochemistry [19:50:49], [20:03:06]. Acetic acid and pyruvic acid are identified as central molecules for the deepest parts of the biosphere and the beginning of complicated biological processes, respectively [20:23:07], [20:51:30].
Autocatalytic Sets
The concept of autocatalytic sets, championed by Stu Kaufman, is crucial. For dynamic stability, patterns in nature must continually renew themselves [21:44:03]. Autocatalysis is a mechanism where outputs of a process are sticky for environmental components, converting them into the same material, thus concentrating and purifying the system [22:46:17]. Biochemistry is replete with such cycles, allowing it to remain integrated in a constantly changing environment [23:01:21].
A key difference in Eric Smith’s approach from Kaufman’s is the emphasis on chemistry as a “structured medium” rather than an unstructured combinatorial one. This requires understanding collective effects and natural feedbacks in highly structured systems like organic chemistry [23:41:09].
Emergence of Life as a Phase Transition
The emergence of life is viewed as a phase transition [07:44:31]. Systems far from equilibrium, unlike stable equilibrium states like a diamond, require energy flow to persist [24:42:00]. This energy flow, or disequilibrium, imposes restrictions on the system’s freedom, leading to greater order [26:30:46]. This aligns with Harold Morowitz’s idea that “the flow of energy through a system tends to organize the system” [27:14:48].
Knowns and Unknowns
While the field has “little islands” of rich information, such as core biochemistry (carbon fixation pathways, citric acid cycle) and the ribosome (an extraordinary repository of history about RNA and early peptides) [29:08:35], [29:32:00], there are vast areas of unknown [29:04:22]. The genetic code is a point of intersection for these islands, and its origin is likely integrated with the process of becoming energetically active and discovering how to fold [30:31:07].
A significant challenge is the “error catastrophe” problem, where high-fidelity information transfer, as seen in DNA with its complex error correction machinery, is crucial for complex evolution [32:30:00]. Before such high-fidelity systems, it’s perplexing how chemical evolution could have advanced to create complex machinery [32:42:47].
According to Herb Simon’s classic arguments, complex systems are created through integral error correction in subsystems, forming “stable intermediate states of assembly” [34:02:59]. In the context of origin of life, this implies looking for “paths of least resistance” in chemistry that allow systems to naturally regress toward their own central tendencies, reducing the burden on central control systems [35:05:07]. Substrate-assisted catalysis, common in RNA and DNA reactions, exemplifies a simpler catalytic environment that could enable the evolution of memory systems [36:19:15].
Frontiers of Research
The next frontier in origin of life research is learning how to explore chemistry more systematically [37:12:12]. Chemistry is a vast combinatorial system, and current search methods are ad-hoc [37:15:26]. There is ongoing work applying deep learning and machine learning, such as “halfway detection” to discover and optimize chemical pathways [38:35:10].
Current work focuses on the interface of organized geochemistry and the deep origins of biology, including the folding of biopolymers and the genetic code [01:24:00]. A meta-question is understanding how systems capable of carrying a lot of information become available without being buried in the heterogeneity of the physical material they are made of [01:26:13].
Implications for Extraterrestrial Life
The understanding of life’s origin has implications for extraterrestrial life and the Fermi paradox. The necessity of high-fidelity information transfer systems, like DNA with its error correction, poses a challenge for life’s emergence [32:42:47]. The question of when full human language (a complex system) came into existence can also provide a “pruning rule” for life’s progression, with estimates ranging from 40,000 to 300,000 years ago [01:11:10]. The “Out of Africa” migration around 65,000 years ago, with no significant genetic backflow, suggests the capability for full language existed prior to that [01:12:20].