A world of seven billion

A doctor holds up the newborn baby of Yang Huiqing, 26, as she undergoes a caesarian section at Ruijin hospital in Shanghai, October 24, 2011. Yang and her husband Chen Yiming, both born under the one-child policy, had their first baby as the world population was about to reach the seven billion mark. REUTERS/Carlos Barria

Residents crowd in a swimming pool to escape the summer heat during a hot weather spell in Daying county of Suining, Sichuan province, China, July 4, 2010. REUTERS/Stringer

Public residential buildings are seen in Po Lam, one of the "satellite towns" in Hong Kong, September 14, 2011. This southern Chinese city is described as a concrete forest, famous for the number of high-rise commercial and residential towers. About 25 percent of the world's tallest 100 residential buildings that stand at least 200 meters tall are in the territory. REUTERS/Bobby Yip

ACombines harvest wheat on the Stephen and Brian Vandervalk farm near Fort MacLeod,, Alberta, September 26, 2011. Wheat is the most important cereal in the world and along with rice and maize accounts for about 73% of world cereal production. Canada is the world's third largest exporter, producing annually an average of over 24 million tonnes. REUTERS/Todd Korol

Motorists crowd at a junction during rush hour in Taipei, October 29, 2009. There are around 8.8 million motorcycles and 4.8 million cars on Taiwan's roads and nearly all motor vehicles and inhabitants are squeezed into a third of the island's area. REUTERS/Nicky Loh

A farmer takes water form a dried-up pond to water his vegetable field on the outskirts of Yingtan, Jiangxi province, December 10, 2007. REUTERS/Stringer

A migrant construction worker checks his mobile phone outside his dormitory after a working shift at the Shanghai World Expo 2010 construction site in Shanghai, April 15, 2009. REUTERS/ Nir Elias

A view of the city skyline from the Shanghai Financial Center building, October 25, 2011. REUTERS/Carlos Barria

Chinese twins Cao Xiaoqiao (R) and her elder sister Cao Daqiao look at each other on the outskirts of Shiqiaozi town in Zhucheng, Shandong province, June 18, 2009. They were born in 1905. REUTERS/Stringer

People hang onto an entrance of a commuter train which will transport them to Jakarta, in Depok, Indonesia's West Java province, Indonesia, May 31, 2010. REUTERS/Crack Palinggi

A malnourished infant lies on the floor in a therapeutic feeding center run by the medical charity Medecins Sans Frontiers (MSF) in the town of Maradi in southern Niger, June 29, 2005. REUTERS/Finbarr O'Reilly/Files

People gather to get water from a huge well in the village of Natwarghad in the western Indian state of Gujarat, June 1, 2003. REUTERS/Amit Dave

Fairgoers play a carnival game at the San Diego County Fair in Del Mar, California, June 29, 2011. REUTERS/Mike Blake

Young sea gypsies play in the water in the centre of their neighbourhood in the Sulawesi Sea in Malaysia's state of Sabah on the Borneo island, February 17, 2009. REUTERS/Bazuki Muhammad

A migrant labourer climbs a ladder on a building near Hongqiao Airport in Shanghai, August 6, 2010. REUTERS/Aly Song

Parents of students sleep on mats laid out on the floor of a gymnasium inside a university campus in Wuhan, central China's Hubei province, September 3, 2007. REUTERS/Stringer

A campsite at a homeless tent city in Sacramento California, March 15, 2009. REUTERS/ Max Whittaker

High rise residential buildings are seen behind a slum in Mumbai, July 20, 2010. REUTERS/Danish Siddiqui

An asylum seeker from Afghanistan waits for his meal during a daily midday food distribution service near the harbour of Calais in northern France, December 1, 2008. REUTERS/Pascal Rossignol

A man fleeing the unrest in Tunisia looks on as he and others arrive at the southern Italian island of Lampedusa, March 30, 2011. REUTERS/Tony Gentile

A Malaysian Chinese family gathers to offer prayers to their ancestors during Qingming Festival or Ancestors Day at a cemetery in Petaling Jaya outside Kuala Lumpur, April 3, 2011. REUTERS/Bazuki Muhammad

A reflection can be seen on a glass barrier in the Top Of The Rock observation deck in front of the Tribute in Light memorial shining behind the Empire State Building marking the ninth anniversary of the September 11 attacks, in New York, September 11, 2010. REUTERS/Lucas Jackson

A migrant worker from Bangladesh shows his empty wallet to the camera as workers gather near a government office in Singapore, February 16, 2009. REUTERS/Vivek Prakash

Laundry hangs outside a student dormitory at a college in Wuhan, Hubei province, China, March 5, 2009. REUTERS/Stringer

A general view of night Moscow is seen from the window of a passenger jet, October 8, 2010. REUTERS/Alexander Demianchuk

Roman Catholic pilgrims press together while following the image of the local saint Our Lady of Nazareth as it is paraded during the annual Cirio de Nazare procession, the country's biggest religious festival, in the city of Belem, at the mouth of the Amazon River, October 11, 2009. REUTERS/Paulo Santos

Students use their books to protect their heads during a earthquake drill inside a ground of the Paranaque National High School in Baclaran, Paranaque city, metro Manila, February 22, 2011. REUTERS/Romeo Ranoco

Fog rolls by early in the morning, near the Dubai Marina construction and residential zone, in Dubai, September 20, 2007. REUTERS/Steve Crisp

Buddhist novice monk Kyaw Thiha plays during heavy rainfall at Shin Ohtama Tharya monastery in Yangon, May 31, 2011. Entering monkhood is a rite of passage for many Myanmar boys, although most of them spend a few days to a few months rather than as a lifetime commitment. REUTERS/Soe Zeya Tun

Sunbathers and roofed wicker beach chairs are seen along the beach on the bay of Travemuende, a popular holiday resort at the Baltic sea near the northern German city of Luebeck, August 5, 2007. REUTERS/Morris Mac Matzen

An overcrowded train approaches as other passengers wait to board at a railway station in Dhaka, November 16, 2010. REUTERS/Andrew Biraj

Antisa Khvichava, 129 years old, rests at her home in the village of Sachino, west of Tbilisi, March 11, 2010. Khvichava claims to be the oldest person in the world. REUTERS/David Mdzinarishvili

A man walks on a pedestrian bridge overlooking traffic in Lagos, Nigeria, September 18, 2006. REUTERS/Akintunde Akinleye

Italy's Member of the European Parliament Licia Ronzulli takes part with her baby in a voting session at the European Parliament in Strasbourg, September 22, 2010. REUTERS/Vincent Kessler

A women walks on a pedestrian bridge in front of a residential building in Beijing, June 10, 2010. REUTERS/Jason Lee

A boy from the cattle herding Mundari tribe smiles early morning in a settlement near Terekeka, Central Equatoria state, south Sudan, January 19, 2011. REUTERS/Goran Tomasevic

A newborn baby rests in a box, listening to music played through earphones in Saca Hospital in Kosice, east Slovakia, May 25, 2011. REUTERS/Petr Josek

People play tennis at a tennis court surrounded by high-rise buildings in downtown Shanghai, November 4, 2010. REUTERS/Carlos Barria

A farmer walks past a terrace of codonopsis pilosula, a traditional Chinese medicine also known as dang shen, in Min county, Gansu province, China, May 31, 2011. REUTERS/Stringer

Nine pairs of twins and a set of triplets pose for a photograph at a state-run school in Kodinji village in the southern Indian city of Kerala, India, July 30, 2009. REUTERS/Arko Datta

Hundreds of commuters pack the Se central subway station during rush hour in Sao Paulo, August 12, 2003. REUTERS/Paulo Whitaker

Job-seekers visit booths of companies at a job fair held for graduates in Nanjing, Jiangsu province, November 20, 2008. REUTERS/Sean Yong

Businessmen speak on the outdoor smoking area of a building in Lisbon, November 18, 2010. REUTERS/Marcelo del Pozo

Seven babies sit in tummy tubs filled with water to cool down after a baby massage class held for young mothers in IJmuiden, north of Haarlem, Netherlands, March 24, 2009. REUTERS/United Photos

Runners fill the street in front of the Tokyo Metropolitan Government Building at the start of the Tokyo Marathon 2009 in Tokyo, March 22, 2009. REUTERS/Franck Robichon/Pool