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64-566: Species diversity is a feature of the park. It provides habitat for 120 species of mammals , 350 species of birds, 310 species of butterflies , 27 species of frogs, chameleons, geckos, and many endangered species. Floristically, the park is among the most diverse forests in East Africa, with more than 1,000 flowering plant species, including 200 species of trees and 104 species of ferns. The northern (low elevation) sector has many species of Guineo-Congolian flora, including two endangered species,

128-708: A supereon , but this is also an informal term, not defined by the ICS in its chronostratigraphic guide. Eozoic (from eo- "earliest") was a synonym for pre-Cambrian , or more specifically Archean . A specific date for the origin of life has not been determined. Carbon found in 3.8 billion-year-old rocks (Archean Eon) from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have been found in Western Australia . Probable fossils 100 million years older have been found in

192-480: A broad neocortex region of the brain, fur or hair , and three middle ear bones . These characteristics distinguish them from reptiles and birds , from which their ancestors diverged in the Carboniferous Period over 300 million years ago. Around 6,400 extant species of mammals have been described and divided into 27 orders . The largest orders of mammals, by number of species , are

256-416: A maximum of 20 to 27 °C (68 to 81 °F). Its annual rainfall ranges from 1,400 to 1,900 mm (55 to 75 in). Peak rainfall occurs from March to April and from September to November. The park's forest plays an important role in regulating the surrounding area's environment and climate. High amounts of evapotranspiration from the forest's vegetation increase the precipitation that the region outside

320-735: A possible 2450 Ma red alga from the Kola Peninsula , 1650 Ma carbonaceous biosignatures in north China, the 1600 Ma Rafatazmia , and a possible 1047 Ma Bangiomorpha red alga from the Canadian Arctic. The earliest fossils widely accepted as complex multicellular organisms date from the Ediacaran Period. A very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota . Hard-shelled creatures appeared toward

384-489: A small understory tree. The mountain gorilla is an endangered species, with an estimated total population of about 650 individuals. There are no mountain gorillas in captivity, but during the 1960s and 1970s, some were captured to start captive breeding. The park is owned by the Uganda Wildlife Authority , a parastatal government body. The park has total protection, although communities adjacent to

448-417: Is Rwamunyonyi Hill at the eastern edge of the park. The lowest part of the park is at its most northern tip. The forest is an important water catchment area. With a generally impermeable underlying geology where water mostly flows through large fault structures, water infiltration and aquifers are limited. Much of the park's rainfall forms streams, and the forest has a dense network of streams. The forest

512-404: Is a continuum of low-altitude to high altitude primary forests in the park, one of the few large tracts of East African forest where this occurs. The park has more than 220 tree species, and more than 50% of Uganda's tree species, and more than 100 fern species. The brown mahogany is a threatened plant species in the park. Bwindi Impenetrable National Park is important for the conservation of

576-563: Is at the edge of the Western Rift Valley in the highest parts of the Kigezi Highlands , which were created by up-warping of the Western Rift Valley. Its topography is very rugged, with narrow valleys intersected by rivers and steep hills. Elevations in the park range from 1,190 to 2,607 m (3,904 to 8,553 ft), and 60 percent of the park has an elevation of over 2,000 m (6,600 ft). The highest elevation

640-480: Is composed of two blocks of forest that are connected by a corridor of forest. The shape of the park is a legacy of previous conservation management, when the original two forest blocks were protected in 1932. There is agricultural land where there were previously trees directly outside the park's borders. Cultivation in this area is intense. The park's underlying geology consists of Precambrian shale phyllite , quartz , quartzite , schist , and granite . The park

704-664: Is known to occur during the RNA replication of extant coronaviruses . Evidence of the details of plate motions and other tectonic activity in the Precambrian is difficult to interpret. It is generally believed that small proto-continents existed before 4280 Ma, and that most of the Earth's landmasses collected into a single supercontinent around 1130 Ma. The supercontinent, known as Rodinia , broke up around 750 Ma. A number of glacial periods have been identified going as far back as

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768-408: Is one of the area's few ways of earning income. Prior to Bwindi's gazetting as a national park in 1991, the park was designated as a forest reserve, and regulations about the right to access the forest were more liberal and seldom enforced. Local people hunted, mined, logged, pit sawed, and kept bees in the park. It was gazetted as a national park in 1991 because of its rich biodiversity and threats to

832-572: Is primarily driven by human poaching and habitat destruction , primarily deforestation . Over 70% of mammal species are in the orders Rodentia , Chiroptera , and Eulipotyphla . Mammal classification has been through several revisions since Carl Linnaeus initially defined the class, and at present , no classification system is universally accepted. McKenna & Bell (1997) and Wilson & Reeder (2005) provide useful recent compendiums. Simpson (1945) provides systematics of mammal origins and relationships that had been taught universally until

896-426: Is the viviparous placental mammals , so named for the temporary organ ( placenta ) used by offspring to draw nutrition from the mother during gestation . Most mammals are intelligent , with some possessing large brains, self-awareness , and tool use . Mammals can communicate and vocalize in several ways, including the production of ultrasound , scent marking , alarm signals , singing , echolocation ; and, in

960-668: Is the earliest part of Earth's history , set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian , the first period of the Phanerozoic Eon , which is named after Cambria , the Latinized name for Wales , where rocks from this age were first studied. The Precambrian accounts for 88% of the Earth's geologic time. The Precambrian is an informal unit of geologic time, subdivided into three eons ( Hadean , Archean , Proterozoic ) of

1024-485: Is the source of many rivers that flow to the north, west, and south. Major rivers that rise in the park include the Ivi , Munyaga , Ihihizo , Ishasha , and Ntengyere rivers, which flow into Lake Edward . Other rivers flow into Lakes Mutanda and Bunyonyi . Bwindi supplies water to local agricultural areas. Bwindi has a tropical climate. Annual mean temperature ranges from a minimum of 7 to 15 °C (45 to 59 °F) to

1088-521: Is thought that the Earth coalesced from material in orbit around the Sun at roughly 4,543 Ma, and may have been struck by another planet called Theia shortly after it formed, splitting off material that formed the Moon (see Giant-impact hypothesis ). A stable crust was apparently in place by 4,433 Ma, since zircon crystals from Western Australia have been dated at 4,404 ± 8 Ma. The term "Precambrian"

1152-731: Is used by geologists and paleontologists for general discussions not requiring a more specific eon name. However, both the United States Geological Survey and the International Commission on Stratigraphy regard the term as informal. Because the span of time falling under the Precambrian consists of three eons (the Hadean , the Archean , and the Proterozoic ), it is sometimes described as

1216-473: The Cretaceous . The relationships between these three lineages is contentious, and all three possible hypotheses have been proposed with respect to which group is basal . These hypotheses are Atlantogenata (basal Boreoeutheria), Epitheria (basal Xenarthra) and Exafroplacentalia (basal Afrotheria). Boreoeutheria in turn contains two major lineages— Euarchontoglires and Laurasiatheria . Estimates for

1280-534: The Huronian epoch, roughly 2400–2100 Ma. One of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a " Snowball Earth ". The atmosphere of the early Earth is not well understood. Most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and

1344-564: The International Union for Conservation of Nature (IUCN) completed a five-year Global Mammal Assessment for its IUCN Red List , which counted 5,488 species. According to research published in the Journal of Mammalogy in 2018, the number of recognized mammal species is 6,495, including 96 recently extinct. The word " mammal " is modern, from the scientific name Mammalia coined by Carl Linnaeus in 1758, derived from

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1408-556: The Latin mamma ("teat, pap"). In an influential 1988 paper, Timothy Rowe defined Mammalia phylogenetically as the crown group of mammals, the clade consisting of the most recent common ancestor of living monotremes ( echidnas and platypuses ) and therian mammals ( marsupials and placentals ) and all descendants of that ancestor. Since this ancestor lived in the Jurassic period, Rowe's definition excludes all animals from

1472-475: The afromontane fauna, especially species endemic to the Western Rift Valley 's mountains. It is thought to have one of the richest faunal communities in East Africa, including more than 350 bird species and more than 200 butterfly species. There are an estimated 120 mammal species in the park, of which 10 are primates , and more than 45 are small mammals. Along with mountain gorilla , species in

1536-606: The biological classification scheme used, are the primates : apes , monkeys , and lemurs ; the Cetartiodactyla : whales and even-toed ungulates ; and the Carnivora which includes cats , dogs , weasels , bears , seals , and allies. According to Mammal Species of the World , 5,416 species were identified in 2006. These were grouped into 1,229  genera , 153  families and 29 orders. In 2008,

1600-539: The brown mahogany and Brazzeia longipedicellata . In particular, the area shares in the high levels of endemisms of the Albertine Rift . The park is a sanctuary for colobus monkeys , chimpanzees , and many birds such as hornbills and turacos . It is most notable for the 400 Bwindi gorillas, half of the world's population of the endangered mountain gorillas . Fourteen mountain gorilla groups live in four different sectors of Buhoma, Ruhijja, Rushaga and

1664-406: The dominant terrestrial animal group from 66 million years ago to the present. The basic mammalian body type is quadrupedal , with most mammals using four limbs for terrestrial locomotion ; but in some, the limbs are adapted for life at sea , in the air , in trees or underground . The bipeds have adapted to move using only the two lower limbs, while the rear limbs of cetaceans and

1728-522: The geologic time scale . It spans from the formation of Earth about 4.6 billion years ago ( Ga ) to the beginning of the Cambrian Period, about 538.8 million years ago ( Ma ), when hard-shelled creatures first appeared in abundance. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earth's history , and what is known has largely been discovered from

1792-482: The oxygen catastrophe . At first, oxygen would have quickly combined with other elements in Earth's crust, primarily iron, removing it from the atmosphere. After the supply of oxidizable surfaces ran out, oxygen would have begun to accumulate in the atmosphere, and the modern high-oxygen atmosphere would have developed. Evidence for this lies in older rocks that contain massive banded iron formations that were laid down as iron oxides. A terminology has evolved covering

1856-428: The rodents , bats , and Eulipotyphla (including hedgehogs , moles and shrews ). The next three are the primates (including humans , monkeys and lemurs ), the even-toed ungulates (including pigs , camels , and whales ), and the Carnivora (including cats , dogs , and seals ). Mammals are the only living members of Synapsida ; this clade , together with Sauropsida (reptiles and birds), constitutes

1920-439: The sea cows are mere internal vestiges . Mammals range in size from the 30–40 millimetres (1.2–1.6 in) bumblebee bat to the 30 metres (98 ft) blue whale —possibly the largest animal to have ever lived. Maximum lifespan varies from two years for the shrew to 211 years for the bowhead whale . All modern mammals give birth to live young, except the five species of monotremes , which lay eggs. The most species-rich group

1984-401: The 1960s onwards. The Precambrian fossil record is poorer than that of the succeeding Phanerozoic , and fossils from the Precambrian (e.g. stromatolites ) are of limited biostratigraphic use. This is because many Precambrian rocks have been heavily metamorphosed , obscuring their origins, while others have been destroyed by erosion, or remain deeply buried beneath Phanerozoic strata. It

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2048-509: The Bwindi gorilla diet is very similar to that of Bwindi chimpanzees. It was also found that Bwindi gorillas travel farther per day than Virunga gorillas, particularly on days when feeding primarily on fruit than when they are feeding on fibrous foods. Additionally, Bwindi gorillas are much more likely to build their nests in trees, nearly always in Alchornea floribunda (locally, "Echizogwa"),

2112-451: The Bwindi population, which makes up almost half of all the mountain gorillas in the world. The rest of the worldwide mountain gorilla population lives in the nearby Virunga Mountains . A 2006 census of the mountain gorilla population in the park showed that its numbers had increased modestly from an estimated 300 individuals in 1997, to 320 individuals in 2002 to 340 individuals in 2006, and 400 in 2018. Poaching , disease and habitat loss are

2176-600: The Nkuringo in the districts of Kanungu, Kabale and Kisoro respectively, all under the management of Uganda Wildlife Authority. In 1932, two blocks of the Bwindi Impenetrable Forest were designated as Crown Forest Reserves. The northern block was designated as the "Kayonza Crown Forest Reserve", and the southern block designated as the "Kasatora Crown Forest Reserve". These reserves had a combined area of 207 square kilometres (80 sq mi). In 1942,

2240-506: The border from the DRC and kidnapped 14 foreign tourists and their Ugandan guide from the park headquarters, eventually releasing six and murdering the remaining eight with machetes and clubs. Several victims were reportedly tortured, and at least one of the female victims was raped. The Ugandan guide was doused with gasoline and lit on fire . The Interahamwe attack was reportedly intended to "destabilize Uganda" and frighten away tourist traffic from

2304-492: The case of humans, complex language . Mammals can organize themselves into fission–fusion societies , harems , and hierarchies —but can also be solitary and territorial . Most mammals are polygynous , but some can be monogamous or polyandrous . Domestication of many types of mammals by humans played a major role in the Neolithic Revolution , and resulted in farming replacing hunting and gathering as

2368-812: The clade originating with the last common ancestor of Sinoconodon and living mammals. The earliest-known synapsid satisfying Kemp's definitions is Tikitherium , dated 225 Ma , so the appearance of mammals in this broader sense can be given this Late Triassic date. However, this animal may have actually evolved during the Neogene. As of the early 21st century, molecular studies based on DNA analysis have suggested new relationships among mammal families. Most of these findings have been independently validated by retrotransposon presence/absence data . Classification systems based on molecular studies reveal three major groups or lineages of placental mammals— Afrotheria , Xenarthra and Boreoeutheria —which diverged in

2432-444: The closest thing to an official classification of mammals, despite its known issues. Most mammals, including the six most species-rich orders , belong to the placental group. The three largest orders in numbers of species are Rodentia : mice , rats , porcupines , beavers , capybaras , and other gnawing mammals; Chiroptera : bats; and Eulipotyphla : shrews , moles , and solenodons . The next three biggest orders, depending on

2496-401: The current scheme based upon numerical ages. Such a system could rely on events in the stratigraphic record and be demarcated by GSSPs . The Precambrian could be divided into five "natural" eons, characterized as follows: The movement of Earth's plates has caused the formation and break-up of continents over time, including occasional formation of a supercontinent containing most or all of

2560-454: The damage they do to local people's property because their fear of people has decreased. [REDACTED] Bwindi Impenetrable National Park travel guide from Wikivoyage Mammal A mammal (from Latin mamma  'breast') is a vertebrate animal of the class Mammalia ( / m ə ˈ m eɪ l i . ə / ). Mammals are characterized by the presence of milk -producing mammary glands for feeding their young,

2624-1490: The divergence times between these three placental groups range from 105 to 120 million years ago, depending on the type of DNA used (such as nuclear or mitochondrial ) and varying interpretations of paleogeographic data. Monotremata Marsupialia Xenarthra Afrotheria Glires Euarchonta [REDACTED] Eulipotyphla Chiroptera Pholidota Carnivora [REDACTED] Perissodactyla [REDACTED] Artiodactyla [REDACTED] Monotremata [REDACTED] Paucituberculata [REDACTED] Didelphimorphia [REDACTED] Microbiotheria Notoryctemorphia [REDACTED] Peramelemorphia [REDACTED] Dasyuromorphia [REDACTED] Diprotodontia [REDACTED] Cingulata [REDACTED] Pilosa [REDACTED] Hyracoidea [REDACTED] Sirenia [REDACTED] Proboscidea [REDACTED] Tubulidentata [REDACTED] Macroscelidea [REDACTED] Afrosoricida [REDACTED] Eulipotyphla [REDACTED] Chiroptera [REDACTED] Pholidota [REDACTED] Carnivora [REDACTED] Perissodactyla [REDACTED] Artiodactyla [REDACTED] Scandentia [REDACTED] Lagomorpha [REDACTED] Precambrian The Precambrian ( / p r i ˈ k æ m b r i . ə n , - ˈ k eɪ m -/ pree- KAM -bree-ən, -⁠KAYM- ; or Pre-Cambrian , sometimes abbreviated pC , or Cryptozoic )

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2688-585: The earlier Triassic , despite the fact that Triassic fossils in the Haramiyida have been referred to the Mammalia since the mid-19th century. If Mammalia is considered as the crown group, its origin can be roughly dated as the first known appearance of animals more closely related to some extant mammals than to others. Ambondro is more closely related to monotremes than to therian mammals while Amphilestes and Amphitherium are more closely related to

2752-453: The early years of the Earth's existence, as radiometric dating has allowed absolute dates to be assigned to specific formations and features. The Precambrian is divided into three eons: the Hadean (4567.3–4031 Ma), Archean (4031-2500 Ma) and Proterozoic (2500-538.8 Ma). See Timetable of the Precambrian . It has been proposed that the Precambrian should be divided into eons and eras that reflect stages of planetary evolution, rather than

2816-705: The end of that time span, marking the beginning of the Phanerozoic Eon. By the middle of the following Cambrian Period, a very diverse fauna is recorded in the Burgess Shale , including some which may represent stem groups of modern taxa. The increase in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life. While land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Tracks from an animal with leg-like appendages have been found in what

2880-451: The end of the 20th century. However, since 1945, a large amount of new and more detailed information has gradually been found: The paleontological record has been recalibrated, and the intervening years have seen much debate and progress concerning the theoretical underpinnings of systematization itself, partly through the new concept of cladistics . Though fieldwork and lab work progressively outdated Simpson's classification, it remains

2944-624: The greatest threat to the gorillas. Research on the Bwindi population lags behind that of the Virunga National Park population, but some preliminary research on the Bwindi gorilla population has been carried out by Craig Stanford . This research has shown that the Bwindi gorilla's diet is markedly higher in fruit than that of the Virunga population, and that the Bwindi gorillas, even silverbacks, are more likely to climb trees to feed on foliage, fruits, and epiphytes . In some months,

3008-510: The integrity of the forest. Its designation as a national park gave the park higher protection status. State agencies increased protection and control of the park. Adjacent communities' access to the forest immediately ended. This closing of access caused large amounts of resentment and conflict among these local communities and park authorities. The Batwa , an ethnic group that had relied on the forest, were badly affected. The Batwa fished, harvested wild yams and honey, and had ancestral sites within

3072-541: The landmass. The earliest known supercontinent was Vaalbara . It formed from proto-continents and was a supercontinent 3.636 billion years ago. Vaalbara broke up c. 2.845–2.803 Ga ago. The supercontinent Kenorland was formed c. 2.72 Ga ago and then broke sometime after 2.45–2.1 Ga into the proto-continent cratons called Laurentia , Baltica , Yilgarn craton and Kalahari . The supercontinent Columbia , or Nuna, formed 2.1–1.8 billion years ago and broke up about 1.3–1.2 billion years ago. The supercontinent Rodinia

3136-668: The larger Amniota clade. Early synapsids are referred to as " pelycosaurs ." The more advanced therapsids became dominant during the Guadalupian . Mammals originated from cynodonts , an advanced group of therapsids, during the Late Triassic to Early Jurassic . Mammals achieved their modern diversity in the Paleogene and Neogene periods of the Cenozoic era, after the extinction of non-avian dinosaurs , and have been

3200-806: The main reserve, increasing its area to almost 321 km (124 sq mi). The park continued to be managed as both a game sanctuary and forest reserve . In 1991, the Impenetrable Central Forest Reserve, along with the Mgahinga Gorilla Reserve and the Rwenzori Mountains Reserve , was designated as a national park and renamed the Bwindi Impenetrable National Park. It covered an area of 330.8 square kilometres (127.7 sq mi). The national park

3264-504: The park can access some of its resources. The areas bordering the park have a high population density of over 300/km (780/sq mi). Some of the people who live in these areas are among the poorest people in Uganda. The high population and poor agricultural practices place great pressure on the Bwindi forest, and are one of the biggest threats to the park. Ninety percent of the people are dependent on subsistence agriculture , as agriculture

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3328-449: The park include common chimpanzee , L'Hoest's monkey , African elephant , African green broadbill , and cream-banded swallowtail , black and white colobus , red-tailed monkeys , vervets , the giant forest hog . The fish species in the park's rivers and streams are not well known. The park is inhabited by about 459 individual mountain gorillas as per the last 2019 Gorilla Census (Gorilla Fund) ( Gorilla beringei beringei ), known as

3392-420: The park receives. It also lessens soil erosion , a serious problem in south-western Uganda. It lessens flooding and ensures that streams continue to flow in the dry season. The Bwindi Impenetrable Forest is old, complex, and biologically rich. Diverse species are a feature of the park, and it became a UNESCO World Heritage Site because of its ecological importance. Among East African forests, Bwindi has some of

3456-480: The park, depriving the Ugandan government of income. The park was forced to close for several months, and the popularity of the gorilla tours suffered badly for several years, though attendance has since recovered due to greater stability in the area. An armed guard also now accompanies every tour group. Kabale town to the south-east is the nearest main town to the park, 29 km (18 mi) away by road. The park

3520-613: The park. Despite the Batwa people's historical claim to land rights and having lived in the area for generations without destroying the area's ecosystem, they did not benefit from any national compensation scheme when they were evicted. Non-Batwa farmers who had cut down the forested areas in order to cultivate them, received compensation and their land rights were recognised. People have lost livestock and crops from wildlife, and there have been some human deaths. The habituation of gorillas to humans in order to facilitate tourism may have increased

3584-716: The primary source of food for humans. This led to a major restructuring of human societies from nomadic to sedentary, with more co-operation among larger and larger groups, and ultimately the development of the first civilizations . Domesticated mammals provided, and continue to provide, power for transport and agriculture, as well as food ( meat and dairy products ), fur , and leather . Mammals are also hunted and raced for sport, kept as pets and working animals of various types, and are used as model organisms in science. Mammals have been depicted in art since Paleolithic times, and appear in literature, film, mythology, and religion. Decline in numbers and extinction of many mammals

3648-574: The richest populations of trees, small mammals, birds, reptiles, butterflies, and moths. The park's diverse species are partly a result of the large variations of elevation and habitat types in the park, and may also be because the forest was a refuge for species during glaciations in the Pleistocene epoch. The park's forests are afromontane , which is a rare vegetation type on the African continent. Located where plain and mountain forests meet, there

3712-526: The same area. However, there is evidence that life could have evolved over 4.280 billion years ago. There is a fairly solid record of bacterial life throughout the remainder (Proterozoic Eon) of the Precambrian. Complex multicellular organisms may have appeared as early as 2100 Ma. However, the interpretation of ancient fossils is problematic, and "... some definitions of multicellularity encompass everything from simple bacterial colonies to badgers." Other possible early complex multicellular organisms include

3776-548: The therians; as fossils of all three genera are dated about 167 million years ago in the Middle Jurassic , this is a reasonable estimate for the appearance of the crown group. T. S. Kemp has provided a more traditional definition: " Synapsids that possess a dentary – squamosal jaw articulation and occlusion between upper and lower molars with a transverse component to the movement" or, equivalently in Kemp's view,

3840-568: The two reserves were combined and enlarged, then renamed the Impenetrable Central Crown Forest. This new protected area covered 298 square kilometres (115 sq mi) and was under the joint control of the Ugandan government's game and forest departments. In 1964, the reserve was designated as an animal sanctuary to provide extra protection for its mountain gorillas and renamed the Impenetrable Central Forest Reserve. In 1966, two other forest reserves became part of

3904-540: Was declared in part to protect a range of species within it, most notably the mountain gorilla. The reclassification of the park had a large impact on the Batwa pygmy people, who were evicted from the forest and no longer permitted to enter the park or access its resources. Gorilla tracking became a tourist activity in April 1993, and the park became a popular tourist destination. In 1994, a 10 km (3.9 sq mi) area

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3968-532: Was incorporated into the park and it was inscribed on the World Heritage List . The park's management changed when Uganda National Parks, since renamed the Uganda Wildlife Authority , became responsible for the park. In 2003, a piece of land next to the park with an area of 4.2 square kilometres (1.6 sq mi) was purchased and incorporated into the park. In March 1999, a force of 100–150 former Rwandan Interahamwe guerrillas infiltrated across

4032-482: Was lacking in free oxygen . There is, however, evidence that an oxygen-rich atmosphere existed since the early Archean. At present, it is still believed that molecular oxygen was not a significant fraction of Earth's atmosphere until after photosynthetic life forms evolved and began to produce it in large quantities as a byproduct of their metabolism . This radical shift from a chemically inert to an oxidizing atmosphere caused an ecological crisis , sometimes called

4096-852: Was mud 551 million years ago. The RNA world hypothesis asserts that RNA evolved before coded proteins and DNA genomes. During the Hadean Eon (4,567–4,031 Ma) abundant geothermal microenvironments were present that may have had the potential to support the synthesis and replication of RNA and thus possibly the evolution of a primitive life form. It was shown that porous rock systems comprising heated air-water interfaces could allow ribozyme - catalyzed RNA replication of sense and antisense strands that could be followed by strand-dissociation, thus enabling combined synthesis, release and folding of active ribozymes. This primitive RNA replicative system also may have been able to undergo template strand switching during replication ( genetic recombination ) as

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