Rusinga Island, with an elongated shape approximately 10 miles (16 km) from end to end and 3 miles (5 km) at its widest point, lies in the eastern part of

Lake Victoria Lake Victoria is one of the African Great Lakes. With a surface area of approximately , Lake Victoria is Africa's largest lake by area, the world's largest tropics, tropical lake, and the world's second-largest fresh water lake by surface are ...

at the mouth of the

Winam Gulf Winam Gulf is a significant extension of northeastern Lake Victoria into western Kenya. Formerly known as Kavirondo Gulf, Nyanza Gulf, and Lake Nyanza Gulf, it is a shallow inlet and is connected to the main lake by Rusinga Channel ( wide), which ...

. Part of

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

, it is linked to Mbita Point on the mainland by the new Rusinga-Mbita bridge which replaced the old causeway.

Demography

The local language is Luo, although the ancestors of the current inhabitants were Suba people who came in boats several hundred years ago from Uganda as refugees from a dynastic war. Many Rusinga place names portray Suba origins, including the island's name itself and its central peak, Lunene. There was an extinct language of Uganda called Singa, alternatives Lusinga and Lisinga, spoken only on Rusinga Island (which, of course is in Kenya). As of 2006, estimates of Rusinga's population ranged between 20,000 and 30,000. The entire island is part of the

Homa Bay County Homa Bay County is a county in the former Nyanza Province of Kenya. Its capital and largest town is Homa Bay. The county has a population of 1,131,950 (2019 census) and an area of 3,154.7 km2. Lake Victoria is a major source of livelihood ...

. Most residents of Rusinga make their living from subsistence agriculture (maize and millet), as well as fishing. The native

tilapia Tilapia ( ) is the common name for nearly a hundred species of cichlid fish from the coelotilapine, coptodonine, heterotilapine, oreochromine, pelmatolapiine, and tilapiine tribes (formerly all were "Tilapiini"), with the economically mos ...

is still caught, though this species (like all others native to the lake) has been decimated by the voracious

Nile perch The Nile perch (''Lates niloticus''), also known as the African snook, Goliath perch, African barramundi, Goliath barramundi, Giant lates or the Victoria perch, is a species of freshwater fish in family Latidae of order Perciformes. It is wides ...

that was introduced into the lake in 1954. Constant onshore winds cool the lakeward side of the island and provide clean beaches with ideal swimming and boating conditions, but poor roads between Rusinga and the nearest town,

Homa Bay Homa Bay is a town (and eponymous bay) on the south shore of Winam Gulf of Lake Victoria, in western Kenya. It lies near Mount Homa (in the Luo language ''Got Marahuma'' or ''God Uma'' famous mountain" and Ruma National Park, the latter note ...

, inhibit trade and tourism. The brightly glittering black sands of the beaches are made of crystals of melanite

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

, barkevikite

hornblende Hornblende is a complex silicate minerals#Inosilicates, inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common ...

, and

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula . It is one of the iron oxide, oxides of iron, and is ferrimagnetism, ferrimagnetic; it is attracted to a magnet and can be magnetization, magnetized to become a ...

eroded from the uncompahgrite lava fragments in the

agglomerate Agglomerate (from the Latin ''agglomerare'' meaning "to form into a ball") is a coarse accumulation of large blocks of volcanic material that contains at least 75% bombs. Volcanic bombs differ from volcanic blocks in that their shape records flui ...

s that overlie the fossil beds. The

island An island or isle is a piece of land, distinct from a continent, completely surrounded by water. There are continental islands, which were formed by being split from a continent by plate tectonics, and oceanic islands, which have never been ...

is also notable as the family home and burial site of

Tom Mboya Thomas Joseph Odhiambo Mboya (15August 19305July 1969) was a Kenyan trade unionist, educator, Pan-Africanist, author, independence activist, and statesman. He was one of the founding fathers of the Republic of Kenya.Kenya Human Rights Commiss ...

, who before his assassination in 1969 was widely pegged as

Jomo Kenyatta Jomo Kenyatta (22 August 1978) was a Kenyan anti-colonial activist and politician who governed Kenya as its Prime Minister from 1963 to 1964 and then as its first President from 1964 to his death in 1978. He played a significant role in the ...

's successor as President of the new nation of Kenya.

Palaeontology

Rusinga is widely known for its extraordinarily rich and important fossil beds of extinct

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

mammals, dated to 18 million years. The island had been only cursorily explored until the Leakey expedition of 1947-1948 began systematic searches and excavations, which have continued sporadically since then. The end of 1948 saw the collection of about 15,000 fossils from the

, including 64

primates Primates is an order of mammals, which is further divided into the strepsirrhines, which include lemurs, galagos, and lorisids; and the haplorhines, which include tarsiers and simians ( monkeys and apes). Primates arose 74–63 ...

called by

Louis Leakey Louis Seymour Bazett Leakey (7 August 1903 – 1 October 1972) was a Kenyan-British palaeoanthropologist and archaeologist whose work was important in demonstrating that humans evolved in Africa, particularly through discoveries made at Olduvai ...

"Miocene apes." All the species of ''

Proconsul A proconsul was an official of ancient Rome who acted on behalf of a Roman consul, consul. A proconsul was typically a former consul. The term is also used in recent history for officials with delegated authority. In the Roman Republic, military ...

'' were among the 64 and all were given the name ''africanus'', although many were reclassified into ''nyanzae'', ''major'' and ''heseloni'' later.

Mary Leakey Mary Douglas Leakey, Fellow of the British Academy, FBA (née Nicol, 6 February 1913 – 9 December 1996) was a British paleoanthropologist who discovered the first fossilised ''Proconsul (mammal), Proconsul'' skull, an extinct ape which is now ...

discovered the first complete skull of Proconsul, then considered a "stem hominoid", in 1948. Excavation of the fossil was completed by Louis' assistant, Heselon Mukiri (whence Walker's 1993 name heseloni). Many thousands of fossils are now known from five major sites, with abundant hominoids including an almost complete skeleton of a second species of ''Proconsul'', as well as ''Nyanzapithecus'', ''Limnopithecus'', ''Dendropithecus'' and ''Micropithecus'', all of which show arboreal rather than terrestrial adaptations. The first true

monkeys Monkey is a common name that may refer to most mammals of the infraorder Simiiformes, also known as simians. Traditionally, all animals in the group now known as simians are counted as monkeys except the apes. Thus monkeys, in that sense, co ...

do not appear until around 15 million years ago, so it is widely supposed that the diverse Early Miocene African catarrhines like those found on Rusinga filled that adaptive niche. The phylogenetic position of these primates has been debated. It has been theorized that ''Proconsul'' is a stem catarrhine and therefore ancestral to both Cercopithecids (Old World monkeys) and

hominids The Hominidae (), whose members are known as the great apes or hominids (), are a taxonomic family of primates that includes eight extant species in four genera: '' Pongo'' (the Bornean, Sumatran and Tapanuli orangutan); '' Gorilla'' (the ...

(great apes and humans), rather than a stem hominoid.

', Harrison T. 1987. "The phylogenetic relationships of the early catarrhine primates: a review of the current evidence." ''Journal of Human Evolution'' 16(1), 41-80

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

mammal fossils, including an extinct

antelope The term antelope refers to numerous extant or recently extinct species of the ruminant artiodactyl family Bovidae that are indigenous to most of Africa, India, the Middle East, Central Asia, and a small area of Eastern Europe. Antelopes do ...

genus, ''

Rusingoryx ''Rusingoryx'' is a genus of extinct alcelaphine bovid artiodactyl closely related to the wildebeest. It contains only one species, ''R. atopocranion'', that lived on the plains of Kenya during the Pleistocene. It was originally named as a speci ...

'', notable for its nasal dome hypothesised to produce loud calls, known nowhere else, are also common in former shoreline deposits around the edges of the island, left behind as Lake Victoria has slowly subsided over the centuries due to erosion in its outlet.

Geology

The fossil beds are layers of volcanic ash produced by a succession of explosive eruptions during the earliest stages of a volcano that eventually covered an area 75 miles in diameter. The volcano is now eroded down to the frozen magma in its vent that makes up the Kisingiri hills on the mainland opposite Rusinga, and the surrounding remnants of the cone: the semicircular Rangwa mountain range, and the islands of Rusinga and neighboring Mfangano Island. This

rift valley A rift valley is a linear shaped lowland between several highlands or mountain ranges produced by the action of a geologic rift. Rifts are formed as a result of the pulling apart of the lithosphere due to extensional tectonics. The linear ...

volcano on the southern flank of the now-inactive Winam Gulf tapped much deeper in the mantle than oceanic or

subduction zone Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...

volcanos, and its lavas and explosive ash clouds thus contained much more carbonate and alkali than normal. This meant that even though the Miocene environment was a tropical rainforest, the chemistry of the successive ash beds was that of a desert dry lake, preserving everything from caterpillars and berries to apes and elephants in an unusual situation found only in a few other East African volcanos, notably

Menengai Menengai Crater is a massive shield volcano with one of the biggest calderas in the world, in the Great Rift Valley, Kenya. It is the largest volcano caldera in Kenya and the second largest volcano caldera in Africa. Volcanic formed rich loam so ...

and Homa Mountain in western Kenya, Napak and

Mount Elgon Mount Elgon is an extinct shield volcano on the border of Uganda and Kenya, north of Kisumu and west of Kitale. The mountain's highest point, named "Wagagai", is located entirely within Uganda.

in Uganda, and the much younger

Ol Doinyo Lengai Ol Doinyo Lengai is an active volcano in northern Tanzania. It consists of a volcanic cone with two craters, the northern of which has erupted during historical time. Uniquely for volcanoes on Earth, it has erupted natrocarbonatite, an unusually ...

in Tanzania, which created the fossil beds of

Olduvai Gorge The Olduvai Gorge or Oldupai Gorge in Tanzania is one of the most important paleoanthropology, paleoanthropological localities in the world; the many sites exposed by the gorge have proven invaluable in furthering understanding of early human evo ...

Notes

External links

GEF RUSINGA ISLAND Projects
United Nations Development Programmes.
Greening Rusinga Island
Africa Now site. *
Palaeoenvironments of Early Miocene Kisingiri volcano Proconsul sites: Evidence from carbon isotopes, palaeosols and hydromagmatic deposits
', article by Erick Bestland and Evelyn S. Krull, ''Journal of the Geological Society'', September, 1999. An extensive abstract of this highly technical article is displayed at no charge.
Living Waters Intl
Since 2006, Living Waters Intl, a faith based non-profit organization, has been providing clean water, medical care, a feeding center, orphan assistance and educational facility upgrades, sustainable vegetable gardens, to the people of Rusinga Island, Kenya, Africa {{Coord, 0, 24, S, 34, 10, E, region:KE_type:isle, display=title Homa Bay County Islands of Lake Victoria Lake islands of Kenya Miocene paleontological sites of Africa

Demography

Palaeontology

Geology

See also

Notes

External links