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Development influences longevity


Chart 1: The average age of Chinese people in ancient times. [ LIU YANFENG/China Daily ]

What is the determinant factor in people's longevity? In an article published in this year's June issue of Xinhua Digest, Professor Zheng Zheng of Nanjing University and Wang Xingping, the curator of Nanjing Museum, jointly probe the question from an interesting angle.

Among the world's four most famous ancient civilizations, the Chinese civilization is the only one that has lasted continually for over 5,000 years.

There are numerous historical documents about the birth and death of famous ancient Chinese figures.

With these precious documents it is possible to find out about ancient Chinese peo-ple's longevity and the elements affecting changes in lifespan.

We mainly relied on "The Annals," "Histories of the Han Dynasty" and 22 other annals of succeeding dynasties in China. We also looked at local chronicles, family records, as well as "Chronicles of Famous Figures across Dynasties" and the "Grand Dictionary of Famous Chinese."

Our collection practices were strict: To be eligible the dates of the person's birth and death had to be unquestionable; He/she had to have died naturally, not been murdered, killed in war, or died suddenly of unknown reasons. We also dismissed a number of figures who lived a long but mystic life.

We gathered the material on over 5,000 people's lifespan from the Qin Dynasty (221-207 BC) to the Qing Dynasty (1644-1911).

The people we cited in the study were in the higher strata of society and their lifespans should have been longer than the common people. But the patterns they represent can be applied to average Chinese people.

As an old Chinese saying goes: "From ancient times until today, it is rare to live above the age of 70." In fact, Chinese people call the age of 70 guxi or rare.

From the curve of longevity shown in chart 1 we find strong proof for this saying. People lived the longest, generally above 75, before the end of the Han Dynasty (206 BC-AD 220). In the following centuries, except for some brief improvements in the Tang (AD 618-907), Ming (1368-1644) and Qing dynasties, most Chinese people did not surpass the age of 70.

The worst time occurred around AD 350, when the average Chinese less than 60 years. That time was during the chaotic period known as the Eastern Jin (AD 317-420), a weak authority struggling with 16 kingdoms set up by different ethnic groups.

With these figures in mind, we are able to proceed into searching for the most relevant elements leading to it.

Ancient China was agricultural. The Chinese used to say "people regard food as heaven." The development of agricultural techniques is closely related with the Chinese life span.

In the Qin and Han dynasties, China was united and the feudal system took shape. The rulers promoted advanced cultivation techniques such as cattle-drawn plows across the country. The Han authorities also reduced taxes to let farmers make greater profits.

In the following years, China was torn by constant warfare. Large areas of cultivated fields were deserted. As a result the level of agriculture hardly advanced.

In the Sui (AD 581-618) and Tang dynasties, the country was once again united. Many water conservation projects were initiated and higher techniques were promoted among farmers.

It is recorded that in eight large cities of that time, the central government set up granaries that stored millet "enough for nine years" and rice "enough for five years" to meet the needs of the local population.

With the uprising of warlords An Lushan (AD 703-757) and Shi Siming (AD 703-761) between 755 and 763, the Tang Dynasty started to decline. The following chaotic period known as "Five Dynasties and 10 Kingdoms (AD 907-960)" plunged China into further devastation. The wars continued throughout the Song Dynasty (960-1279), although the cultivation of rice increased during this time.

When Mongolian rulers united China in the Yuan Dynasty (1271-1368), Kublai Khan (1215-94) realized the importance of agriculture and encouraged cultivation and forbade forced labour during busy farming seasons.

As the Chinese population increased during the Ming and Qing dynasties, budding capitalism also brought better cultivation techniques to farmers. The introduction of corn, sweet potatoes, peanuts and other food crops from the New World in the 16th century also gave rise to agricultural output.

In Chart 2, we present the variation of crop yields per mu (0.06 hectare) and the per capita food consumption through the 2,000 years from the Han to Qing dynasties to give the above accounts statistical support.

We derived most of the figures from the book, "Research on Yield Per Mu of Each Chinese Dynasty" written by Wu Hui of the Economy Institute with the Chinese Academy of Social Sciences.

To determine the figures on cultivated lands in the Qing Dynasty is rather complicated.

Some researchers say that less than 66 million hectares of land were cultivated in this period. But our research went against this assumption.

Qing rulers encouraged the people to cultivate every bit of land, including mountains and lakes. At its height, the Qing empire covered a territory of 13 million square kilometres, much bigger than today's China, at 9.6 million square kilometres.

In addition, desertification and construction have reduced a great deal of cultivated lands in today's China. Thus, we judge that the area of cultivated lands in the Qing Dynasty was at least similar to the figure in today's China, at about 133 million hectares.

Considering many elements, we calculated the per capita food cultivation area in the Qing Dynasty to be 0.29 hectares.

In chart 3, we put together the figures on people's longevity, crop yields per mu (0.06 hectares) and per capita food consumption.

From chart 2 and 3, we can see that the crop yield per mu (0.06 hectares) was rising gradually. It demonstrates the increasing level of agriculture techniques, but also indicates that the increase was limited — in 2,000 years, the crop yield per mu (0.06 hectares) only grew by 51.5 kilogrammes.

Accordingly, per capita food consumption also only slowly grew from 500 kilogrammes to 770 kilogrammes.

People's longevity did not grow as much as the other two elements. Obviously, there is something more to consider.

The crop yield figures in chart 2 are from normal harvest years, without considering natural disasters.

Floods, drought, hail, locusts and other natural disasters had great impact. History books often talk about the hardship resulting from natual disasters.

From records in the 24 annals, the "Table of Natural Disasters and Man-made Calamities in Each Dynasty," and the "History of Disaster Rescues in China," we formed chart 4 of disasters in the main dynasties.

This chart shows that the frequency of natural disasters rose at a stunning rate — 15 times more in the Qing Dynasty than the Han period.

Besides warfare, cultivation was the main reason for this disaster increase. From the less than 20 million population in the early Han Dynasty, the Chinese population had grown to more than several hundred million in the Qing Dynasty. The area of cultivated land also expanded from 2 million hectares to about 133 million hectares, an increase of over 60 times.

Under increasing population pressure, cultivation was forced to become more labour intensive and also expand into the sandy loams, arid hills and the upper reaches of lofty mountains.

In an edict of 1740, Emperor Qianlong, who ruled from 1736-1796, noted that "the population is constantly increasing, while the land does not become any more extensive." He directed his subjects to cultivate all and every piece of soil.

With more forests and lakes depleted, natural disasters occurred more often.

Added to the frequency of natural disasters, we drew chart 5 to show the relationship between ancient Chinese people's longevity and per capita food consumption.

Except for the Northern and Southern Dynasties (AD 420-581), the two figures coincide with each other very well. This suggests that per capita food consumption is the determining factor affecting longevity in ancient China.

First, the agriculture production as represented in crop yields per mu (0.06 hectares) kept increasing from the Han to Qing dynasties. But the increase was limited to about 50 kilogrammes.

Despite occasional technical improvements in later periods, there were no major breakthroughs in mechanical or chemical technology after the Han Dynasty. The production tools, cultivation system and methods were followed until the Qing Dynasty.

The rapid increase of population led to growing cultivation, which in turn led to the deterioration of the environment. Ever more frequent natural disasters kept the actual per capita food consumption low. The quantity of food basically determined people's life span.

In about 335 BC, the Chinese philosopher Mencius wrote: "If the farmer's seasons are not interfered with, there will be more grain in the land than can be consumed."

These facts will surely provide useful insights for today.

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