生命の起源の衝撃的な挫折
1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena 91125, USA.
Nature
|February 18, 1988
まとめ
地球上の生命の起源は,アビオゲネシスの時間スケールよりもインパクトが少なくなった時間によって定義されることがあります. 深海の熱水噴出孔は,生命が4000~4億2千万年前に始まった可能性を示唆しています.
科学分野:
- 天体生物学 アストロバイオロジー
- 地質学 地質学 地質学
- 生命の起源の研究 生命の起源の研究
背景:
- ハーデア紀と初期のアーケイア紀は,激しい小惑星の衝突によって特徴づけられました.
- アビオゲネシス,つまり無機物質から生命の誕生は,地球の歴史における重要な出来事です.
研究 の 目的:
- 衝撃の頻度とアビオゲネシスの時間スケールに基づいて生命の起源を定義する.
- アビオゲネシスが異なる初期の地球環境で発生した時期を推定する.
主な方法:
- 月面と地上の衝突記録を分析して,ハデアン時代と初期アーケアン時代の衝突フックスを定量化します.
- 提案されたアビオゲネシス環境に対する衝撃関連のプロセスの影響を推定する.
- 衝撃間隔と環境適合性に基づいて,アビオゲネシスの潜在的な時間枠を計算する.
主要な成果:
- アビオゲネシスは,深海の熱水環境で,4,000~4,200億年前に既に発生した可能性がある.
- 地球の表面では,アビオゲネシスは3700~4000万年前に発生した可能性がある.
- 自己複製原生物を確立するための時間軸は,重要な要因です.
結論:
- 生命の起源のタイミングは,壊滅的な衝撃の頻度の低下によって制限されています.
- 水熱噴出孔と地表の位置など,異なる初期の地球環境は,アビオゲネシスのタイミングの明確な可能性を提供します.
関連する概念動画
01:29Life Histories
Constrained by limited energy and resources, organisms must compromise between offspring quantity and parental investment. This trade-off is represented by two primary reproductive strategies; K-strategists produce few offspring but provide substantial parental support, whereas r-strategists produce much progeny that receives little care. These strategies are related to an organism’s survival likelihood across its lifespan, which is represented by a survivorship curve. Three general types of...
01:50Threats to Biodiversity
There have been five major extinction events throughout geological history, resulting in the elimination of biodiversity, followed by a rebound of species that adapted to the new conditions. In the current geological epoch, the Holocene, there is a sixth extinction event in progress. This mass extinction has been attributed to human activities and is thus provisionally called the Anthropocene. In 2019 the human population reached 7.7 billion people and is projected to comprise 10 billion by...
03:33Genetic Drift
Natural selection—probably the most well-known evolutionary mechanism—increases the prevalence of traits that enhance survival and reproduction. However, evolution does not merely propagate favorable traits, nor does it always benefit populations.Life is not fair. A deer grazing contentedly in a field can have her meal cut tragically short by a bolt of lightning. If the doomed doe is one of only three in the population, 1/3 of the population’s gene pool is lost. Random events like this can...
01:30Impact
Impact occurs when two bodies collide, leading to the application of impulsive forces between them. Analyzing impact mechanics involves considering two colliding particles moving along a line known as the line of impact, which passes through their centers and is perpendicular to the contact plane.
When particles with different initial velocities collide, they induce deformation by applying equal and opposite impulses. At the point of maximum deformation, the particles move together with...
When particles with different initial velocities collide, they induce deformation by applying equal and opposite impulses. At the point of maximum deformation, the particles move together with...
01:24Origin of Cellular Life
The origin of life on Earth is a complex and enigmatic event rooted in ancient biochemical processes and geological conditions. Experimental evidence supports the hypothesis that life began with the spontaneous formation of organic molecules such as RNA nucleotides, amino acids, and lipids under early Earth conditions. Factors like volcanic activity, intense UV radiation, and a reducing atmosphere without free oxygen likely facilitated these reactions. Hydrothermal vents on the ocean floor are...
01:26Origin of Photosynthesis
Photosynthesis represents a fundamental biological process that transformed Earth's atmosphere and paved the way for complex life. Emerging roughly 3.4–3.8 billion years ago, the earliest photosynthetic organisms harnessed light energy to produce organic compounds. These anoxygenic phototrophs used electron donors like hydrogen sulfide (H₂S) or ferrous iron (Fe²⁺), rather than water, and did not release molecular oxygen (O₂) as a byproduct. Various groups, including green sulfur and purple...