Warm little pond

=== Oparin–Haldane hypothesis ===

=== Oparin–Haldane hypothesis ===

The general idea of a warm little pond-like environment was subsequently echoed in abiogenesis theories following this initial proposal, notably the Oparin–Haldane theory. While it is unclear if he was aware of Darwin's 1871 letter, Soviet biochemist [[Alexander Oparin]] was known to subscribe to the Darwinian theory of evolution, which was widely accepted in Russia at the time.{{Cite journal |last=Lazcano |first=Antonio |date=2016-12-01 |title=Alexandr I. Oparin and the Origin of Life: A Historical Reassessment of the Heterotrophic Theory |journal=Journal of Molecular Evolution |language=en |volume=83 |issue=5 |pages=214–222 |doi=10.1007/s00239-016-9773-5 |pmid=27896387 |bibcode=2016JMolE..83..214L |s2cid=253782021 |issn=1432-1432}} In 1924, he published a booklet, ''The Origin of Life'', suggesting a scenario in which commonly available [[Volatility (chemistry)|volatiles]] would have been oxidized in the early atmosphere to form various hydrocarbons such as alcohols, ketones, and aldehydes. After precipitation into [[seawater]], these may have reacted to form complex biomolecules, and eventually given rise to the first cells.{{Cite book |last=Oparin |first=A. I. |url=https://discovery.nationalarchives.gov.uk/details/r/e5de3de8-4b25-4229-a186-e68a7d43f5ef |title=Translation (by Ann Synge) of The Origin of Life on the Earth by A.I. Oparin |date=1958 |language=English}} This idea is often referred to as the [[Heterotroph|heterotrophic]] origin of life, as it suggests the first organisms obtained energy and carbon from organic molecules as opposed to carbon dioxide (CO_2).{{Cite journal |last1=Schönheit |first1=Peter |last2=Buckel |first2=Wolfgang |last3=Martin |first3=William F. |date=2016 |title=On the Origin of Heterotrophy |journal=Trends in Microbiology |volume=24 |issue=1 |pages=12–25 |doi=10.1016/j.tim.2015.10.003 |pmid=26578093 |bibcode=2016TrMic..24...12S |issn=0966-842X}}

The general idea of a warm little pond-like environment was subsequently echoed in abiogenesis theories following this initial proposal, notably the Oparin–Haldane theory. While it is unclear if he was aware of Darwin's 1871 letter, Soviet biochemist [[Alexander Oparin]] was known to subscribe to the Darwinian theory of evolution, which was widely accepted in Russia at the time.{{Cite journal |last=Lazcano |first=Antonio |date=2016-12-01 |title=Alexandr I. Oparin and the Origin of Life: A Historical Reassessment of the Heterotrophic Theory |journal=Journal of Molecular Evolution |language=en |volume=83 |issue=5 |pages=214–222 |doi=10.1007/s00239-016-9773-5 |pmid=27896387 |bibcode=2016JMolE..83..214L |s2cid=253782021 |issn=1432-1432}} In 1924, he published a booklet, ''The Origin of Life'', suggesting a scenario in which commonly available [[Volatility (chemistry)|volatiles]] would have been oxidized in the early atmosphere to form various hydrocarbons such as alcohols, ketones, and aldehydes. After precipitation into [[seawater]], these may have reacted to form complex biomolecules, and eventually given rise to the first cells.{{Cite book |last=Oparin |first=A. I. |url=https://discovery.nationalarchives.gov.uk/details/r/e5de3de8-4b25-4229-a186-e68a7d43f5ef |title=Translation (by Ann Synge) of The Origin of Life on the Earth by A.I. Oparin |date=1958 |language=English}} This idea is often referred to as the [[Heterotroph|heterotrophic]] origin of life, as it suggests the first organisms obtained energy and carbon from organic molecules as opposed to [[carbon dioxide]] (CO_2).{{Cite journal |last1=Schönheit |first1=Peter |last2=Buckel |first2=Wolfgang |last3=Martin |first3=William F. |date=2016 |title=On the Origin of Heterotrophy |journal=Trends in Microbiology |volume=24 |issue=1 |pages=12–25 |doi=10.1016/j.tim.2015.10.003 |pmid=26578093 |bibcode=2016TrMic..24...12S |issn=0966-842X}}

Oparin's idea was formulated independently from and prior to [[J. B. S. Haldane|J. B. S. Haldane's]] proposal for the origin of life, which suggested in 1929 that ultraviolet induced [[photochemistry]] may have produced simple organics from a mixture of CO_2 and ammonia (NH_3) in the young oceans. These substances would have increased in concentration, eventually forming a primordial soup that provided a platform and ample feedstocks for the prebiotic chemistry leading to the first lifeforms. Eventually, this early life would have utilized and depleted these organics until it became capable of synthesizing them itself.{{Cite journal |last=Haldane |first=J. B. S. |date=1929 |title=The Origin of Life |url=https://www.uv.es/~orilife/textos/Haldane.pdf |journal=The Rationalist Annual |pages=3–10}} While there are some distinctions between the two ideas related to the nature of the first [[metabolism]], due to their similarities and simultaneity, the joining of these theories is referred to as the Oparin–Haldane hypothesis for the origin of life.{{Cite journal |last=Tirard |first=Stéphane |date=2017-11-01 |title=J. B. S. Haldane and the origin of life |journal=Journal of Genetics |language=en |volume=96 |issue=5 |pages=735–739 |doi=10.1007/s12041-017-0831-6 |pmid=29237880 |s2cid=255488816 |issn=0973-7731}}

Oparin's idea was formulated independently from and prior to [[J. B. S. Haldane|J. B. S. Haldane's]] proposal for the origin of life, which suggested in 1929 that ultraviolet induced [[photochemistry]] may have produced simple organics from a mixture of CO_2 and ammonia (NH_3) in the young oceans. These substances would have increased in concentration, eventually forming a primordial soup that provided a platform and ample feedstocks for the prebiotic chemistry leading to the first lifeforms. Eventually, this early life would have utilized and depleted these organics until it became capable of synthesizing them itself.{{Cite journal |last=Haldane |first=J. B. S. |date=1929 |title=The Origin of Life |url=https://www.uv.es/~orilife/textos/Haldane.pdf |journal=The Rationalist Annual |pages=3–10}} While there are some distinctions between the two ideas related to the nature of the first [[metabolism]], due to their similarities and simultaneity, the joining of these theories is referred to as the Oparin–Haldane hypothesis for the origin of life.{{Cite journal |last=Tirard |first=Stéphane |date=2017-11-01 |title=J. B. S. Haldane and the origin of life |journal=Journal of Genetics |language=en |volume=96 |issue=5 |pages=735–739 |doi=10.1007/s12041-017-0831-6 |pmid=29237880 |s2cid=255488816 |issn=0973-7731}}

Wet–dry cycles can serve as a mechanism to concentrate reactants, generate gradients in temperature or pH, and drive both [[Dehydration reaction|dehydration]] and [[hydrolysis]] reactions, which are favorable under dry conditions and in solution respectively.{{Cite journal |last1=Walton |first1=Craig |last2=Rimmer |first2=Paul B. |last3=Williams |first3=Helen |last4=Shorttle |first4=Oliver |date=2020-11-10 |title=Prebiotic Chemistry in the Wild: How Geology Interferes with the Origins of Life |doi=10.26434/chemrxiv.13198205.v1 |doi-access=free }} Environmental fluctuations may have produced these cycles in early terrestrial environments, which have been shown to bring about a wide range of organic mixtures whose compositions vary with conditions such as pH and salinity.{{Cite journal |last1=Foster |first1=Kiernan |last2=Hillman |first2=Brooke |last3=Rajaei |first3=Vahab |last4=Seng |first4=Kimsorn |last5=Maurer |first5=Sarah |date=2022 |title=Evolution of Realistic Organic Mixtures for the Origins of Life through Wet–Dry Cycling |journal=Sci |language=en |volume=4 |issue=2 |page=22 |doi=10.3390/sci4020022 |issn=2413-4155 |doi-access=free }}

Wet–dry cycles can serve as a mechanism to concentrate reactants, generate gradients in temperature or pH, and drive both [[Dehydration reaction|dehydration]] and [[hydrolysis]] reactions, which are favorable under dry conditions and in solution respectively.{{Cite journal |last1=Walton |first1=Craig |last2=Rimmer |first2=Paul B. |last3=Williams |first3=Helen |last4=Shorttle |first4=Oliver |date=2020-11-10 |title=Prebiotic Chemistry in the Wild: How Geology Interferes with the Origins of Life |doi=10.26434/chemrxiv.13198205.v1 |doi-access=free }} Environmental fluctuations may have produced these cycles in early terrestrial environments, which have been shown to bring about a wide range of organic mixtures whose compositions vary with conditions such as pH and salinity.{{Cite journal |last1=Foster |first1=Kiernan |last2=Hillman |first2=Brooke |last3=Rajaei |first3=Vahab |last4=Seng |first4=Kimsorn |last5=Maurer |first5=Sarah |date=2022 |title=Evolution of Realistic Organic Mixtures for the Origins of Life through Wet–Dry Cycling |journal=Sci |language=en |volume=4 |issue=2 |page=22 |doi=10.3390/sci4020022 |issn=2413-4155 |doi-access=free }}

Wet–dry cycling may have resulted from a number of different mechanisms in different environments, including hot spring or geyser action, evaporative cycles, seasonal climactic cycles, or daily weather cycles. Temporally, cycles may range from minutes to weeks depending on their driver. The action of wet–dry cycles is key to the hot spring hypothesis for the origin of life, which suggests protocells developed through a multistep process in which spontaneously formed [[Vesicle (biology and chemistry)|lipid vesicles]] incorporate polymers that grow through [[Condensation reaction|condensation reactions]]. It has been furthermore suggested that the interactions between these cells as a gel-like substance during the transition between each cycle could have constituted a precursor to multicellular life.{{Cite journal |last1=Damer |first1=Bruce |last2=Deamer |first2=David |date=2020 |title=The Hot Spring Hypothesis for an Origin of Life |journal=Astrobiology |volume=20 |issue=4 |pages=429–452 |doi=10.1089/ast.2019.2045 |issn=1531-1074 |pmc=7133448 |pmid=31841362|bibcode=2020AsBio..20..429D }} It has been shown that small peptides can self assemble during the dehydration phase in the presence of fatty acid micelles,{{Cite journal |last1=Cohen |first1=Zachary R. |last2=Kessenich |first2=Brennan L. |last3=Hazra |first3=Avijit |last4=Nguyen |first4=Julia |last5=Johnson |first5=Richard S. |last6=MacCoss |first6=Michael J. |last7=Lalic |first7=Gojko |last8=Black |first8=Roy A. |last9=Keller |first9=Sarah L. |date=2022-02-04 |title=Prebiotic Membranes and Micelles Do Not Inhibit Peptide Formation During Dehydration |journal=ChemBioChem |volume=23 |issue=3 |article-number=e202100614 |doi=10.1002/cbic.202100614 |issn=1439-7633 |pmc=8957845 |pmid=34881485}} and that fatty acid and phospholipid vesicles can retain their contents during this phase.{{Cite journal |last1=Cohen |first1=Zachary R. |last2=Cornell |first2=Caitlin. E. |last3=Catling |first3=David C. |last4=Black |first4=Roy A. |last5=Keller |first5=Sarah L. |date=2022-01-25 |title=Prebiotic Protocell Membranes Retain Encapsulated Contents during Flocculation, and Phospholipids Preserve Encapsulation during Dehydration |url=https://pubs.acs.org/doi/10.1021/acs.langmuir.1c03296 |journal=Langmuir |language=en |volume=38 |issue=3 |pages=1304–1310 |doi=10.1021/acs.langmuir.1c03296 |pmid=35026114 |s2cid=245952021 |issn=0743-7463|url-access=subscription }}

Wet–dry cycling may have resulted from a number of different mechanisms in different environments, including hot spring or geyser action, evaporative cycles, seasonal climactic cycles, or daily weather cycles. Temporally, cycles may range from minutes to weeks depending on their driver. The action of wet–dry cycles is key to the hot spring hypothesis for the origin of life, which suggests protocells developed through a multistep process in which spontaneously formed [[Vesicle (biology and chemistry)|lipid vesicles]] incorporate polymers that grow through [[Condensation reaction|condensation reactions]]. It has been furthermore suggested that the interactions between these cells as a gel-like substance during the transition between each cycle could have constituted a precursor to multicellular life.{{Cite journal |last1=Damer |first1=Bruce |last2=Deamer |first2=David |date=2020 |title=The Hot Spring Hypothesis for an Origin of Life |journal=Astrobiology |volume=20 |issue=4 |pages=429–452 |doi=10.1089/ast.2019.2045 |issn=1531-1074 |pmc=7133448 |pmid=31841362|bibcode=2020AsBio..20..429D }} It has been shown that small peptides can self assemble during the dehydration phase in the presence of [[fatty acid]] micelles,{{Cite journal |last1=Cohen |first1=Zachary R. |last2=Kessenich |first2=Brennan L. |last3=Hazra |first3=Avijit |last4=Nguyen |first4=Julia |last5=Johnson |first5=Richard S. |last6=MacCoss |first6=Michael J. |last7=Lalic |first7=Gojko |last8=Black |first8=Roy A. |last9=Keller |first9=Sarah L. |date=2022-02-04 |title=Prebiotic Membranes and Micelles Do Not Inhibit Peptide Formation During Dehydration |journal=ChemBioChem |volume=23 |issue=3 |article-number=e202100614 |doi=10.1002/cbic.202100614 |issn=1439-7633 |pmc=8957845 |pmid=34881485}} and that fatty acid and [[phospholipid]] vesicles can retain their contents during this phase.{{Cite journal |last1=Cohen |first1=Zachary R. |last2=Cornell |first2=Caitlin. E. |last3=Catling |first3=David C. |last4=Black |first4=Roy A. |last5=Keller |first5=Sarah L. |date=2022-01-25 |title=Prebiotic Protocell Membranes Retain Encapsulated Contents during Flocculation, and Phospholipids Preserve Encapsulation during Dehydration |url=https://pubs.acs.org/doi/10.1021/acs.langmuir.1c03296 |journal=Langmuir |language=en |volume=38 |issue=3 |pages=1304–1310 |doi=10.1021/acs.langmuir.1c03296 |pmid=35026114 |s2cid=245952021 |issn=0743-7463|url-access=subscription }}

There is some theoretical and experimental evidence for [[nucleobase]] formation and stability in warm little ponds as well, possibly preceding the hypothetical [[RNA world]] stage of chemical evolution. One possibility is the exogenous delivery of simple organics ranging from amino acids{{Cite journal |last1=Meierhenrich |first1=Uwe J. |last2=Muñoz Caro |first2=Guillermo M. |last3=Bredehöft |first3=Jan Hendrik |last4=Jessberger |first4=Elmar K. |last5=Thiemann |first5=Wolfram H.-P. |date=2004-06-11 |title=Identification of diamino acids in the Murchison meteorite |journal=Proceedings of the National Academy of Sciences |volume=101 |issue=25 |pages=9182–9186 |doi=10.1073/pnas.0403043101 |pmid=15194825 |pmc=438950 |bibcode=2004PNAS..101.9182M |issn=0027-8424 |doi-access=free }} to nucleobases{{Cite journal |last1=Callahan |first1=Michael P. |last2=Smith |first2=Karen E. |last3=Cleaves |first3=H. James |last4=Ruzicka |first4=Josef |last5=Stern |first5=Jennifer C.|author5-link=Jennifer Stern |last6=Glavin |first6=Daniel P. |last7=House |first7=Christopher H. |last8=Dworkin |first8=Jason P. |date=2011-08-11 |title=Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases |journal=Proceedings of the National Academy of Sciences |volume=108 |issue=34 |pages=13995–13998 |doi=10.1073/pnas.1106493108 |pmid=21836052 |issn=0027-8424 |doi-access=free |pmc=3161613 |bibcode=2011PNAS..10813995C }} via carbonaceous meteorites (such as the [[Murchison meteorite]]), after which seasonal wet–dry cycles would lead to the onset of polymerization into [[nucleotide]]s and eventually RNA. Numerical modeling has suggested RNA could have appeared after just several of these cycles.{{Cite journal |last1=Pearce |first1=Ben K. D. |last2=Pudritz |first2=Ralph E. |last3=Semenov |first3=Dmitry A. |last4=Henning |first4=Thomas K. |date=2017-10-24 |title=Origin of the RNA world: The fate of nucleobases in warm little ponds |journal=Proceedings of the National Academy of Sciences |language=en |volume=114 |issue=43 |pages=11327–11332 |doi=10.1073/pnas.1710339114 |issn=0027-8424 |pmc=5664528 |pmid=28973920 |arxiv=1710.00434 |bibcode=2017PNAS..11411327P |doi-access=free }}

There is some theoretical and experimental evidence for [[nucleobase]] formation and stability in warm little ponds as well, possibly preceding the hypothetical [[RNA world]] stage of chemical evolution. One possibility is the exogenous delivery of simple organics ranging from amino acids{{Cite journal |last1=Meierhenrich |first1=Uwe J. |last2=Muñoz Caro |first2=Guillermo M. |last3=Bredehöft |first3=Jan Hendrik |last4=Jessberger |first4=Elmar K. |last5=Thiemann |first5=Wolfram H.-P. |date=2004-06-11 |title=Identification of diamino acids in the Murchison meteorite |journal=Proceedings of the National Academy of Sciences |volume=101 |issue=25 |pages=9182–9186 |doi=10.1073/pnas.0403043101 |pmid=15194825 |pmc=438950 |bibcode=2004PNAS..101.9182M |issn=0027-8424 |doi-access=free }} to nucleobases{{Cite journal |last1=Callahan |first1=Michael P. |last2=Smith |first2=Karen E. |last3=Cleaves |first3=H. James |last4=Ruzicka |first4=Josef |last5=Stern |first5=Jennifer C.|author5-link=Jennifer Stern |last6=Glavin |first6=Daniel P. |last7=House |first7=Christopher H. |last8=Dworkin |first8=Jason P. |date=2011-08-11 |title=Carbonaceous meteorites contain a wide range of extraterrestrial nucleobases |journal=Proceedings of the National Academy of Sciences |volume=108 |issue=34 |pages=13995–13998 |doi=10.1073/pnas.1106493108 |pmid=21836052 |issn=0027-8424 |doi-access=free |pmc=3161613 |bibcode=2011PNAS..10813995C }} via carbonaceous meteorites (such as the [[Murchison meteorite]]), after which seasonal wet–dry cycles would lead to the onset of polymerization into [[nucleotide]]s and eventually RNA. Numerical modeling has suggested RNA could have appeared after just several of these cycles.{{Cite journal |last1=Pearce |first1=Ben K. D. |last2=Pudritz |first2=Ralph E. |last3=Semenov |first3=Dmitry A. |last4=Henning |first4=Thomas K. |date=2017-10-24 |title=Origin of the RNA world: The fate of nucleobases in warm little ponds |journal=Proceedings of the National Academy of Sciences |language=en |volume=114 |issue=43 |pages=11327–11332 |doi=10.1073/pnas.1710339114 |issn=0027-8424 |pmc=5664528 |pmid=28973920 |arxiv=1710.00434 |bibcode=2017PNAS..11411327P |doi-access=free }}