Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
Paraguay the Republic of Paraguay, is a country of South America. It is bordered by Argentina to the south and southwest, Brazil to the east and northeast, Bolivia to the northwest. Although it is one of the only two landlocked countries in South America, the country has coasts and ports on the Paraguay and Paraná rivers that give exit to the Atlantic Ocean through the Paraná-Paraguay Waterway. Due to its central location in South America, it is sometimes referred to as Corazón de Sudamérica. Spanish conquistadores arrived in 1524 after navigating northwards from the Río de la Plata to the Paraná River, up the Paraguay River. In 1537, they established the city of Asunción, the first capital of the Governorate of Paraguay and Río de la Plata. Paraguay was the epicenter of the Jesuit Missions, where the Guaraní people were educated and introduced to Christianity and European culture under the direction of the Society of Jesus in Jesuit reductions during the 17th century. However, after the expulsion of the Jesuits from Spanish territories in 1767, Paraguay became a peripheral colony, with few urban centers and settlers.
Following independence from Spain at the beginning of the 19th century, Paraguay was ruled by a series of authoritarian governments who implemented nationalist and protectionist policies. This period ended with the disastrous Paraguayan War, during which Paraguay lost at least 50% of its prewar population and around 25–33% of its territory to the Triple Alliance of Argentina and Uruguay. In the 20th century, Paraguay faced another major international conflict – the Chaco War – against Bolivia, from which the Paraguayans emerged victorious. Afterwards, the country entered a period of military dictatorships, ending with the 35 year regime of Alfredo Stroessner that lasted until he was toppled in 1989 by an internal military coup; this marked the beginning of the "democratic era" of Paraguay. With around 7 million inhabitants, Paraguay is a founding member of Mercosur, an original member of the United Nations, the Organization of American States, the Non-Aligned Movement and the Lima Group; the city of Luque, in Asuncion's Metropolitan Area, is the seat of the CONMEBOL.
The Guarani culture is influential and more than 90% of the people speak different forms of the Guarani language on top of Spanish. Paraguayans are known for being a happy and easy-living people and many times the country topped the "world's happiest place" charts because of the "positive experiences" lived and expressed by the population; the indigenous Guaraní had been living in eastern Paraguay for at least a millennium before the arrival of the Spanish. Western Paraguay, the Gran Chaco, was inhabited by nomads of whom the Guaycuru peoples were the most prominent; the Paraguay River was the dividing line between the agricultural Guarani people to the east and the nomadic and semi-nomadic people to the west in the Gran Chaco. The Guarcuru nomads were known for their warrior traditions and were not pacified until the late 19th century; these indigenous tribes belonged to five distinct language families, which were the bases of their major divisions. Differing language speaking groups were competitive over resources and territories.
They were further divided into tribes by speaking languages in branches of these families. Today 17 separate ethnolinguistic groups remain; the first Europeans in the area were Spanish explorers in 1516. The Spanish explorer Juan de Salazar de Espinosa founded the settlement of Asunción on 15 August 1537; the city became the center of a Spanish colonial province of Paraguay. An attempt to create an autonomous Christian Indian nation was undertaken by Jesuit missions and settlements in this part of South America in the eighteenth century, which included portions of Uruguay and Brazil, they developed Jesuit reductions to bring Guarani populations together at Spanish missions and protect them from virtual slavery by Spanish settlers and Portuguese slave raiders, the Bandeirantes. In addition to seeking their conversion to Christianity. Catholicism in Paraguay was influenced by the indigenous peoples; the reducciones flourished in eastern Paraguay for about 150 years, until the expulsion of the Jesuits by the Spanish Crown in 1767.
The ruins of two 18th-century Jesuit Missions of La Santísima Trinidad de Paraná and Jesús de Tavarangue have been designated as World Heritage Sites by UNESCO. In western Paraguay Spanish settlement and Christianity were resisted by the nomadic Guaycuru and other nomads from the 16th century onward. Most of these peoples were absorbed into the mestizo population in the 19th centuries. Paraguay overthrew the local Spanish administration on 14 May 1811. Paraguay's first dictator was José Gaspar Rodríguez de Francia who ruled Paraguay from 1814 until his death in 1840, with little outside contact or influence, he intended to create a utopian society based on the French theorist Jean-Jacques Rousseau's Social Contract. Rodríguez de Francia established new laws that reduced the powers of the Catholic church and the cabinet, forbade colonial citizens from marrying one another and allowed them to marry only blacks, mulattoes or natives, in order to break the power of colonial-era elites and to create a mixed-race or mestizo society.
He cut off the rest of South America. Because of Francia's restrictions of freedom, Fulgencio Yegros and several other Independence-era
Peru the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, in the west by the Pacific Ocean. Peru is a megadiverse country with habitats ranging from the arid plains of the Pacific coastal region in the west to the peaks of the Andes mountains vertically extending from the north to the southeast of the country to the tropical Amazon Basin rainforest in the east with the Amazon river. Peruvian territory was home to several ancient cultures. Ranging from the Norte Chico civilization in the 32nd century BC, the oldest civilization in the Americas and one of the five cradles of civilization, to the Inca Empire, the largest state in pre-Columbian America, the territory now including Peru has one of the longest histories of civilization of any country, tracing its heritage back to the 4th millennia BCE; the Spanish Empire conquered the region in the 16th century and established a viceroyalty that encompassed most of its South American colonies, with its capital in Lima.
Peru formally proclaimed independence in 1821, following the military campaigns of José de San Martín and Simón Bolívar, the decisive battle of Ayacucho, Peru secured independence in 1824. In the ensuing years, the country enjoyed relative economic and political stability, which ended shortly before the War of the Pacific with Chile. Throughout the 20th century, Peru endured armed territorial disputes, social unrest, internal conflicts, as well as periods of stability and economic upswing. Alberto Fujimori was elected to the presidency in 1990. Fujimori left the presidency in 2000 and was charged with human rights violations and imprisoned until his pardon by President Pedro Pablo Kuczynski in 2017. After the president's regime, Fujimori's followers, called Fujimoristas, have caused political turmoil for any opposing faction in power causing Pedro Pablo Kuczynski to resign in March 2018; the sovereign state of Peru is a representative democratic republic divided into 25 regions. It is classified as an emerging market with a high level of human development and an upper middle income level with a poverty rate around 19 percent.
It is one of the region's most prosperous economies with an average growth rate of 5.9% and it has one of the world's fastest industrial growth rates at an average of 9.6%. Its main economic activities include mining, manufacturing and fishing; the country forms part of The Pacific Pumas, a political and economic grouping of countries along Latin America's Pacific coast that share common trends of positive growth, stable macroeconomic foundations, improved governance and an openness to global integration. Peru ranks high in social freedom. Peru has a population of 32 million, which includes Amerindians, Europeans and Asians; the main spoken language is Spanish, although a significant number of Peruvians speak Quechua or other native languages. This mixture of cultural traditions has resulted in a wide diversity of expressions in fields such as art, cuisine and music; the name of the country may be derived from Birú, the name of a local ruler who lived near the Bay of San Miguel, Panama City, in the early 16th century.
When his possessions were visited by Spanish explorers in 1522, they were the southernmost part of the New World yet known to Europeans. Thus, when Francisco Pizarro explored the regions farther south, they came to be designated Birú or Perú. An alternative history is provided by the contemporary writer Inca Garcilaso de la Vega, son of an Inca princess and a conquistador, he said the name Birú was that of a common Indian happened upon by the crew of a ship on an exploratory mission for governor Pedro Arias de Ávila, went on to relate more instances of misunderstandings due to the lack of a common language. The Spanish Crown gave the name legal status with the 1529 Capitulación de Toledo, which designated the newly encountered Inca Empire as the province of Peru. Under Spanish rule, the country adopted the denomination Viceroyalty of Peru, which became Republic of Peru after independence; the earliest evidences of human presence in Peruvian territory have been dated to 9,000 BC. Andean societies were based on agriculture, terracing.
Organization relied on reciprocity and redistribution because these societies had no notion of market or money. The oldest known complex society in Peru, the Norte Chico civilization, flourished along the coast of the Pacific Ocean between 3,000 and 1,800 BC; these early developments were followed by archaeological cultures that developed around the coastal and Andean regions throughout Peru. The Cupisnique culture which flourished from around 1000 to 200 BC along what is now Peru's Pacific Coast was an example of early pre-Incan culture; the Chavín culture that developed from 1500 to 300 BC was more of a religious than a political phenomenon, with their religious centre in Chavín de Huantar. After the decline of the Chavin culture around the beginning of the 1st century AD, a series of localized and specialized cultures rose and fell
Carnivora is a diverse scrotiferan order that includes over 280 species of placental mammals. Its members are formally referred to as carnivorans, whereas the word "carnivore" can refer to any meat-eating organism. Carnivorans are the most diverse in size of any mammalian order, ranging from the least weasel, at as little as 25 g and 11 cm, to the polar bear, which can weigh up to 1,000 kg, to the southern elephant seal, whose adult males weigh up to 5,000 kg and measure up to 6.7 m in length. Carnivorans have teeth and claws adapted for catching and eating other animals. Many hunt in are social animals, giving them an advantage over larger prey; some carnivorans, such as cats and pinnipeds, depend on meat for their nutrition. Others, such as raccoons and bears, are more omnivorous, depending on the habitat; the giant panda is a herbivore, but feeds on fish and insects. The polar bear subsists on seals. Carnivorans are split into two suborders: Caniformia. Carnivorans all share the same arrangement of teeth in which the last upper premolar and the first lower molar have blade-like enamel crowns that work together as carnassial teeth to shear meat.
Carnivorans have had this arrangement for over 60 million years with many adaptions, these dental adaptions help identify carnivoran species and groupings of species. Carnivorans evolved in North America out of members of the family Miacidae about 42 million years ago, they soon split into dog-like forms. Their molecular phylogeny shows the extant Carnivora are a monophyletic group, the crown group of the Carnivoramorpha. Most carnivorans are terrestrial; the last premolar of the upper jaw and first molar of the lower are termed the carnassials or sectorial teeth. These blade-like teeth occlude with a scissor-like action for shredding meat. Carnassials are most developed in the Felidae and the least developed in the Ursidae. Carnivorans have two conical canines in each jaw; the only two exceptions to this are the sea otter, which has four incisors in the lower jaw, the sloth bear, which has four incisors in the upper jaw. The number of molars and premolars is variable between carnivoran species, but all teeth are rooted and are diphyodont.
Incisors are retained by carnivorans and the third incisor is large and sharp. Carnivorans have either four or five digits on each foot, with the first digit on the forepaws known as the dew claw, being vestigial in most species and absent in some; the superfamily Canoidea – Canidae, Mustelidae, Ursidae, Otariidae and Phocidae and the extinct family Amphicyonidae – are characterized by having nonchambered or chambered auditory bullae, nonretractable claws, a well-developed baculum. Most species are rather plain in coloration, lacking the flashy spotted or rosetted coats like many species of felids and viverrids have; this is because Canoidea tend to range in the temperate and subarctic biomes, although Mustelidae and Procyonidae have a few tropical species. Most are terrestrial. All families except the Canidae and a few species of Mustelidae are plantigrade. Diet is varied and most tend to be omnivorous to some degree, thus the carnassial teeth are less specialized. Canoidea have more molars in an elongated skull.
The superfamily Feloidea – Felidae, Herpestidae, Hyaenidae and Eupleridae, as well as the extinct family Nimravidae – have spotted, rosetted or striped coats, tend to be more brilliantly colored than their Canoidean counterparts. This is because these species tend to range in tropical habitats, although a few species do inhabit temperate and subarctic habitats. Many are arboreal or semiarboreal, the majority are digitigrade. Diet tends to be more carnivorous in the family Felidae, they have fewer teeth and shorter skulls, with much more specialized carnassials meant for shearing meat. Feliformia claws are retractile, or semiretractile; the terminal phalanx, with the claw attached, folds back in the forefoot into a sheath by the outer side of the middle phalanx of the digit, is retained in this position when at rest by a strong elastic ligament. In the hindfoot, the terminal joint or phalanx is retracted on to the top, not the side of the middle phalanx. Deep flexor muscles straighten the terminal phalanges, so the claws protrude from their sheaths, the soft "velvety" paw becomes converted into a formidable weapon.
The habitual retraction of the claws preserves their points from wear. The superfamily Pinnipedia, now considered to be part of Caniformia, are medium to large aquatic mammals. Being homeothermic marine mammals, pinni
A fossil is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, petrified wood, coal, DNA remnants; the totality of fossils is known as the fossil record. Paleontology is the study of fossils: their age, method of formation, evolutionary significance. Specimens are considered to be fossils if they are over 10,000 years old; the oldest fossils are around 3.48 billion years old to 4.1 billion years old. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils; the development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host. There are many processes that lead to fossilization, including permineralization and molds, authigenic mineralization and recrystallization, adpression and bioimmuration.
Fossils vary in size from one-micrometre bacteria to dinosaurs and trees, many meters long and weighing many tons. A fossil preserves only a portion of the deceased organism that portion, mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates. Fossils may consist of the marks left behind by the organism while it was alive, such as animal tracks or feces; these types of fossil are called trace ichnofossils, as opposed to body fossils. Some fossils are called chemofossils or biosignatures; the process of fossilization varies according to external conditions. Permineralization is a process of fossilization; the empty spaces within an organism become filled with mineral-rich groundwater. Minerals precipitate from the groundwater; this process can occur in small spaces, such as within the cell wall of a plant cell. Small scale permineralization can produce detailed fossils. For permineralization to occur, the organism must become covered by sediment soon after death, otherwise decay commences.
The degree to which the remains are decayed when covered determines the details of the fossil. Some fossils consist only of skeletal teeth; this is a form of diagenesis. In some cases, the original remains of the organism dissolve or are otherwise destroyed; the remaining organism-shaped hole in the rock is called an external mold. If this hole is filled with other minerals, it is a cast. An endocast, or internal mold, is formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve or snail or the hollow of a skull; this is a special form of mold formation. If the chemistry is right, the organism can act as a nucleus for the precipitation of minerals such as siderite, resulting in a nodule forming around it. If this happens before significant decay to the organic tissue fine three-dimensional morphological detail can be preserved. Nodules from the Carboniferous Mazon Creek fossil beds of Illinois, USA, are among the best documented examples of such mineralization.
Replacement occurs. In some cases mineral replacement of the original shell occurs so and at such fine scales that microstructural features are preserved despite the total loss of original material. A shell is said to be recrystallized when the original skeletal compounds are still present but in a different crystal form, as from aragonite to calcite. Compression fossils, such as those of fossil ferns, are the result of chemical reduction of the complex organic molecules composing the organism's tissues. In this case the fossil consists of original material, albeit in a geochemically altered state; this chemical change is an expression of diagenesis. What remains is a carbonaceous film known as a phytoleim, in which case the fossil is known as a compression. However, the phytoleim is lost and all that remains is an impression of the organism in the rock—an impression fossil. In many cases, however and impressions occur together. For instance, when the rock is broken open, the phytoleim will be attached to one part, whereas the counterpart will just be an impression.
For this reason, one term covers the two modes of preservation: adpression. Because of their antiquity, an unexpected exception to the alteration of an organism's tissues by chemical reduction of the complex organic molecules during fossilization has been the discovery of soft tissue in dinosaur fossils, including blood vessels, the isolation of proteins and evidence for DNA fragments. In 2014, Mary Schweitzer and her colleagues reported the presence of iron particles associated with soft tissues recovered from dinosaur fossils. Based on various experiments that studied the interaction of iron in haemoglobin with blood vessel tissue they proposed that solution hypoxia coupled with iron chelation enhances the stability and preservation of soft tissue and provides the basis for an explanation for the unforeseen preservation of fossil soft tissues. However, a older study based on eight taxa ranging in time from the Devonian to the Jurassic found that reasonably well-preserved fibrils that represent collagen were preser
South America is a continent in the Western Hemisphere in the Southern Hemisphere, with a small portion in the Northern Hemisphere. It may be considered a subcontinent of the Americas, how it is viewed in the Spanish and Portuguese-speaking regions of the Americas; the reference to South America instead of other regions has increased in the last decades due to changing geopolitical dynamics. It is bordered on the west on the north and east by the Atlantic Ocean, it includes twelve sovereign states, a part of France, a non-sovereign area. In addition to this, the ABC islands of the Kingdom of the Netherlands and Tobago, Panama may be considered part of South America. South America has an area of 17,840,000 square kilometers, its population as of 2016 has been estimated at more than 420 million. South America ranks fourth in fifth in population. Brazil is by far the most populous South American country, with more than half of the continent's population, followed by Colombia, Argentina and Peru. In recent decades Brazil has concentrated half of the region's GDP and has become a first regional power.
Most of the population lives near the continent's western or eastern coasts while the interior and the far south are sparsely populated. The geography of western South America is dominated by the Andes mountains. Most of the continent lies in the tropics; the continent's cultural and ethnic outlook has its origin with the interaction of indigenous peoples with European conquerors and immigrants and, more locally, with African slaves. Given a long history of colonialism, the overwhelming majority of South Americans speak Portuguese or Spanish, societies and states reflect Western traditions. South America occupies the southern portion of the Americas; the continent is delimited on the northwest by the Darién watershed along the Colombia–Panama border, although some may consider the border instead to be the Panama Canal. Geopolitically and geographically all of Panama – including the segment east of the Panama Canal in the isthmus – is included in North America alone and among the countries of Central America.
All of mainland South America sits on the South American Plate. South America is home to Angel Falls in Venezuela. South America's major mineral resources are gold, copper, iron ore and petroleum; these resources found in South America have brought high income to its countries in times of war or of rapid economic growth by industrialized countries elsewhere. However, the concentration in producing one major export commodity has hindered the development of diversified economies; the fluctuation in the price of commodities in the international markets has led to major highs and lows in the economies of South American states causing extreme political instability. This is leading to efforts to diversify production to drive away from staying as economies dedicated to one major export. South America is one of the most biodiverse continents on earth. South America is home to many interesting and unique species of animals including the llama, piranha, vicuña, tapir; the Amazon rainforests possess high biodiversity, containing a major proportion of the Earth's species.
Brazil is the largest country in South America, encompassing around half of the continent's land area and population. The remaining countries and territories are divided among three regions: The Andean States, the Guianas and the Southern Cone. Traditionally, South America includes some of the nearby islands. Aruba, Curaçao, Trinidad and the federal dependencies of Venezuela sit on the northerly South American continental shelf and are considered part of the continent. Geo-politically, the island states and overseas territories of the Caribbean are grouped as a part or subregion of North America, since they are more distant on the Caribbean Plate though San Andres and Providencia are politically part of Colombia and Aves Island is controlled by Venezuela. Other islands that are included with South America are the Galápagos Islands that belong to Ecuador and Easter Island, Robinson Crusoe Island, Chiloé and Tierra del Fuego. In the Atlantic, Brazil owns Fernando de Noronha and Martim Vaz, the Saint Peter and Saint Paul Archipelago, while the Falkland Islands are governed by the United Kingdom, whose sovereignty over the islands is disputed by Argentina.
South Georgia and the South Sandwich Islands may be associate
Costa Rica the Republic of Costa Rica, is a country in Central America, bordered by Nicaragua to the north, the Caribbean Sea to the northeast, Panama to the southeast, the Pacific Ocean to the southwest, Ecuador to the south of Cocos Island. It has a population of around 5 million in a land area of 51,060 square kilometers. An estimated 333,980 people live in the capital and largest city, San José with around 2 million people in the surrounding metropolitan area; the sovereign state of Costa Rica is a unitary presidential constitutional republic. It is known for its long-standing and stable democracy, for its educated workforce, most of whom speak English; the country spends 6.9% of its budget on education, compared to a global average of 4.4%. Its economy, once dependent on agriculture, has diversified to include sectors such as finance, corporate services for foreign companies and ecotourism. Many foreign manufacturing and services companies operate in Costa Rica's Free Trade Zones where they benefit from investment and tax incentives.
Costa Rica was facing a market liquidity crisis in 2017 due to a growing budget deficit. By August 2017, the Treasury was having difficulty paying its obligations. Other challenges facing the country in its attempts to improve the economy by increasing foreign investment include a poor infrastructure and a need to improve public sector efficiency. Costa Rica was sparsely inhabited by indigenous peoples before coming under Spanish rule in the 16th century, it remained a peripheral colony of the empire until independence as part of the First Mexican Empire, followed by membership in the United Provinces of Central America, from which it formally declared independence in 1847. Since Costa Rica has remained among the most stable and progressive nations in Latin America. Following the brief Costa Rican Civil War, it permanently abolished its army in 1949, becoming one of only a few sovereign nations without a standing army; the country has performed favorably in the Human Development Index, placing 69th in the world as of 2015, among the highest of any Latin American nation.
It has been cited by the United Nations Development Programme as having attained much higher human development than other countries at the same income levels, with a better record on human development and inequality than the median of the region. Costa Rica has progressive environmental policies, it is the only country to meet all five UNDP criteria established to measure environmental sustainability. It was ranked 42nd in the world, third in the Americas, in the 2016 Environmental Performance Index, was twice ranked the best performing country in the New Economics Foundation's Happy Planet Index, which measures environmental sustainability, was identified by the NEF as the greenest country in the world in 2009. Costa Rica plans to become a carbon-neutral country by 2021. By 2016, 98.1% of its electricity was generated from green sources hydro, solar and biomass. Historians have classified the indigenous people of Costa Rica as belonging to the Intermediate Area, where the peripheries of the Mesoamerican and Andean native cultures overlapped.
More pre-Columbian Costa Rica has been described as part of the Isthmo-Colombian Area. Stone tools, the oldest evidence of human occupation in Costa Rica, are associated with the arrival of various groups of hunter-gatherers about 10,000 to 7,000 years BCE in the Turrialba Valley; the presence of Clovis culture type spearheads and arrows from South America opens the possibility that, in this area, two different cultures coexisted. Agriculture became evident in the populations, they grew tubers and roots. For the first and second millennia BCE there were settled farming communities; these were small and scattered, although the timing of the transition from hunting and gathering to agriculture as the main livelihood in the territory is still unknown. The earliest use of pottery appears around 2,000 to 3,000 BCE. Shards of pots, cylindrical vases, platters and other forms of vases decorated with grooves and some modelled after animals have been found; the impact of indigenous peoples on modern Costa Rican culture has been small compared to other nations, since the country lacked a strong native civilization to begin with.
Most of the native population was absorbed into the Spanish-speaking colonial society through inter-marriage, except for some small remnants, the most significant of which are the Bribri and Boruca tribes who still inhabit the mountains of the Cordillera de Talamanca, in the southeastern part of Costa Rica, near the frontier with Panama. The name la costa rica, meaning "rich coast" in the Spanish language, was in some accounts first applied by Christopher Columbus, who sailed to the eastern shores of Costa Rica during his final voyage in 1502, reported vast quantities of gold jewelry worn by natives; the name may have come from conquistador Gil González Dávila, who landed on the west coast in 1522, encountered natives, appropriated some of their gold. During most of the colonial period, Costa Rica was the southernmost province of the Captaincy General of Guatemala, nominally part of the Viceroyalty of New Spain. In practice, the captaincy general was a autonomous entity within the Spanish Empire.
Costa Rica's distance from the capital of the captaincy in Guatemala, its legal prohibition under Spanish law from trade with its southern neighbor Panama part of the Viceroyalty of New Granada, lack of r