Showing posts with label fertility. Show all posts
Showing posts with label fertility. Show all posts

Neanderthals and Denisovans had Fertile Offspring



Interbreeding occurred between Denisovans and Neanderthals. The genetic map shows the impact of this. Faults in genetic makeup has shown there was a fertility cost of interbreedin between different ancestral groups. Neanderthals were not restricted to western Europe. A fossil from an adolescent shows Denisovans and Neanderthals interbred in the Denisova cave region of Russia.

Interbreeding occurred Denisovans Neanderthals. genetic map shows impact this. Faults genetic makeup shown fertility cost interbreedin different ancestoral groups. Modern humans interbred Denisovans 00 generations bred Neanderthals. Interbreeding associated reduced male fertility. Denisovan DN peaks Oceania, surprising amount found South Asians. Denisovan genes associated acute sense smell. Papua New Guinea Denisovan

Researchers analysed DN 257 individuals 20 different non-African populations world traces ancestry Neanderthals Denisovans — another group ancient humans lived same time — modern human genome. Previous studies shown present-day non-African people possess Neanderthal DNA, people, particularly people Oceania, Denisovan DNA. males happened carry Denisovan Neanderthal DN sections [of genome] successful terms producing offspring others. Professor David Reich analysis, published Current Biology, indicated modern humans interbred Denisovans 00 generations trysts Neanderthals.

hybridisation reduced male fertility according evidence significantly lower Denisovan Neanderthal ancestry X chromosome genes highly expressed testes tissues. "They're exactly parts genome would expect deficient infertility males hybrids," study co-author Professor David Reich Harvard Medical School. " would reflect males happened carry Denisovan Neanderthal DN sections successful terms producing offspring others, those sections removed first handful generations mixture occurred." "scars infertility" genetic history, relevant fertility populations contain mix ancestry today, Professor Reich said. 'Surprisingly high' Denisovan ancestry south Asia

showing peak Denisovan ancestry New Guinea — confirming found recent studies — Professor Reich colleagues found surprisingly concentration Denisovan genes individuals south Asia, Himalayas south-central India. " thought perhaps Denisovan ancestry somewhere intermediate east Asians west Eurasians ancestry mix that, didn't that," Professor Reich said. This unexpected result forced researchers rethink Denisovans moved Asia Eurasia. Denisovan genome map. Professor Reich theories emerging explain finding Denisovan ancestry south Asia. "One is actually independent encounter modern humans Denisovan somewhere Eurasian mainland contributed extra Denisovan ancestry people live today south Asia," said.

theory proposes Denisovan DN modern humans comes single encounter point history, hybrids encounter spread region, east south Asia New Guinea Australia. " subsequent mixture diluted Denisovan ancestry mainland, dilution occurred different extents, explaining variability today," Professor Reich said. team's genetic analysis added understanding impact Denisovan ancestry, suggestion Denisovan genes linked subtle sense smell.
Cheese found in tomb

Pioneers Had More Children

People living in different places "breed" at different rates. Reasons put forward are level of income, education of women and access to contraceptives. Family size has also changed at various places in history. The adventurous ones who ventured far and wide had more children than those who remained in established urban centers. This is particularly the case for British and French settlers in North America.

Resources were more plentiful in new unsettled regions. For example, buffalo and native animals could easily be shot and eaten on the spot. New settlers were also healthier, being active for most of their lives. An examination of Canadian records since 1608 shows that couples on the outer edge of expansion had 20 per cent more children than those remaining in established regions. They also married younger. The pioneer contribution to the gene pool was four time greater than those who settled in populated areas. Church records were the main data source. If the number of illegitimate children were known the gene pool contribution could have been even higher.

Human growth in new expanses of virgin land is consistent with plant and animals. Weeds grow vigorously on new accessible land. Larger plants soon take hold as do small animals. The small animals also attract larger animals. Over time as life becomes denser reproduction rates decline. Saying that pioneers in the West grew like weeds is close to the truth. The spread of Mankind across the globe is no accident. It seems to be an evolutionary imperative.
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