Free Newsletters - Space - Defense - Environment - Energy - Solar - Nuclear
..
. Earth Science News .




FLORA AND FAUNA
Smaller families increases descendant wealth but reduces evolutionary success
by Staff Writers
London, UK (SPX) Sep 04, 2012


File image.

Scientists have taken a step closer to solving one of life's mysteries - why family size generally falls as societies become richer. Evolutionary biologists have long puzzled over this because natural selection is expected to have selected for organisms that try to maximise their reproduction. But in industrialised societies around the world, increasing wealth coincides with people deliberately limiting their family size - the so-called 'demographic transition'.

In a study published in Proceedings of the Royal Society B: Biological Sciences, researchers from the London School of Hygiene and Tropical Medicine, the Centre for Health Equity Studies (Stockholm University/Karolinska Institutet) and UCL (University College London) reject a popular theory put forward to explain the phenomenon.

This 'adaptive' hypothesis proposes that low fertility may boost evolutionary success in the long term by increasing offspring wealth, which in turn eventually increases the number of long-term descendants because richer offspring end up having more children.

The researchers found that having a small number of children increased the economic success and social position of descendants across up to four generations, but reduced the total number of long-term descendants.

They conclude that the decision to limit family size can be understood as a strategic choice to improve the socioeconomic success of children and grandchildren in modern societies, but this socioeconomic benefit does not necessarily translate into an evolutionary benefit.

The study indicates a conflict in modern societies between behaviours promoting social and economic benefits versus biological success. This contrasts with traditional populations in the developing world, where behaviours that promote wealth and social status usually lead individuals to leave behind more genetic descendants.

The researchers tested these hypotheses using data from the Uppsala Multigenerational Birth Cohort Study, which tracks 14,000 people born in Sweden in the early 1900s and all their descendants to the present day.

They measured the socioeconomic success of each generation by looking at their school marks, at whether they went to university and at their household income across adulthood. Reproductive success was assessed by survival to adulthood, marriage before age 40 (a proxy for 'mating success') and fertility (number of offspring up to 2009).

Among both male and female children in the original cohort, smaller family size and higher parental socioeconomic position were both associated with substantially higher school marks, university entrance and income. These effects were particularly large when low fertility and high socioeconomic status coincided, with the benefits of small family size being particularly marked in wealthier groups. Moreover, these advantages were in turn passed on to the grandchild and great-grandchild generations.

But contrary to the adaptive hypothesis, small family size and high parental wealth either did not affect reproductive success beyond the first generation of offspring or if anything showed a negative effect in subsequent generations.

Lead author Dr Anna Goodman, Research Fellow at the London School of Hygiene and Tropical Medicine, said: "Under natural selection, you would expect organisms to use their resources to produce more genetic descendants, and so increase their Darwinian fitness. The demographic transition is a puzzle because at first sight it doesn't look like people are doing this.

One adaptive explanation for the puzzle is that there exists a quantity-quality trade-off, such that having more children leads to those children being less able to reproduce in turn - i.e. higher 'quantity' leads to lower biological 'quality'. However our study found this quantity-quality trade off only applied to descendants' socioeconomic success, not their reproductive success."

Co-author Dr David Lawson, from the Department of Anthropology at UCL, said: "One of our most interesting findings is that being from an initially wealthy household makes the benefits of small family size even bigger. Poorer households in contrast have relatively little to gain by limiting fertility, perhaps because the success of their children is more determined by broader societal factors, rather than investment and inheritance from parents, which is in short supply.

This observation suggests a certain economic rationality to fertility patterns in the modern world, since fertility rates often drop first and most substantially in the wealthier sections of society when populations undergo demographic transition."

Professor Ilona Koupil, from the Centre for Health Equity Studies (Stockholm University/Karolinska Institutet) said: "It is important to note the equity implications of these findings. First, this research indicates that differences in family size may have lasting consequences on social inequalities.

Second, this research provides evidence for the fact that people's educational levels and wealth not only affect schoolmarks and income in their children but also in their grandchildren and great-grandchildren. From a broader social policy perspective, our findings show that even in a country like Sweden with relatively low levels of inequality, we need policies that seek to equalise children's opportunities across families."

Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society. A Goodman, I Koupil, D Lawson. Proceedings B. doi: 10.1098/rspb.2012.1415

.


Related Links
London School of Hygiene and Tropical Medicine
Darwin Today At TerraDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





FLORA AND FAUNA
Ancient genome reveals its secrets
Leipzig, Germany (SPX) Sep 04, 2012
The analyses of an international team of researchers led by Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, show that the genetic variation of Denisovans was extremely low, suggesting that although they were present in large parts of Asia, their population was never large for long periods of time. In addition, a comprehensive list documents the g ... read more


FLORA AND FAUNA
Congo, China, sign 975m-euro deal to rebuild Brazzaville

Obama hails govt response to Isaac 'devastation'

Post-Fukushima meeting calls for more work on nuclear safety

Romney off-message in storm-ravaged Bayou

FLORA AND FAUNA
Russia unveils own 'almost Android' system

China's Baidu to invest $1.6 bn in cloud computing

Samsung violates Chinese workers' rights: report

Apple event invites hint at iPhone 5 debut

FLORA AND FAUNA
Coral scientists use new model to find where corals are most likely to survive climate change

Increased Sediment and Nutrients Delivered to Bay as Susquehanna Reservoirs Near Sediment Capacity

Super-trawler cleared to fish in Australian waters

Viruses Could be the Key to Healthy Corals

FLORA AND FAUNA
Major world interests at stake in Canada's vast Mackenzie River Basin

Study suggests large methane reservoirs beneath Antarctic ice sheet

NASA's IceBridge Seeking New View of Changing Sea Ice

Netherlands: Arctic energy rules needed

FLORA AND FAUNA
Discovery may help protect crops from stressors

Uncoiling the cucumber's enigma

Brazil's Rousseff vows to stand firm on environment defense

World can increase food supply, study says

FLORA AND FAUNA
Dakar floods uncover ancient tools, jewellery: researchers

Scripps Researchers Pinpoint Hot Spots as Earthquake Trigger Points

Hundreds of homes damaged in Philippines quake

Earthquake Hazards Map Study Finds Deadly Flaws, MU Researcher Suggests Improvements

FLORA AND FAUNA
Liberia gets Norwegian security training

Uganda seizes LRA munitions

AMISOM troops retake Somalia's Marka port

Sudan, South Sudan dispute Abyei region

FLORA AND FAUNA
DNA of ancient human decoded

Electronics, living tissue, merged in lab

Man mistakes son for monkey, shoots him dead

More Clues About Why Chimps and Humans Are Genetically Different




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement