Write factor affecting the sex ratio.
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sexy girls are the main factor affecting the sex ratio
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the sex ratio in humans is approximately 1:1. Due to higher female fetal mortality,[2] the sex ratio at birth worldwide is commonly thought to be 107 boys to 100 girls,[3] although this value is subject to debate in the scientific community. The sex ratio for the entire world population is 102 males to 100 females (2017 est.).[4]Depending upon which definition is used, between 0.1% and 1.7% of live births are intersex.[5][6]
Gender imbalance may arise as a consequence of various factors including natural factors, exposure to pesticides and environmental contaminants,[7][8] war casualties, sex-selective abortions, infanticides, aging, and deliberate gendercide.
Human sex ratios, either at birth or in the population as a whole, are reported in any of four ways: the ratio of males to females, the ratio of females to males, the proportion of males, or the proportion of females.
If there are 108,000 males and 100,000 females the ratio of males to females is 1.080 and the proportion of males is 51.9%. Scientific literature often uses the proportion of males. This article uses the ratio
In the United States, the sex ratios at birth over the period 1970–2002 were 1.05 for the white non-Hispanic population, 1.04 for Mexican Americans, 1.03 for African Americans and Indians, and 1.07 for mothers of Chinese or Filipino ethnicity.[14] Among Western European countries c. 2001, the ratios ranged from 1.04 in Belgium to 1.07 in Switzerland,[15] Italy,[16] Ireland[17] and Portugal. In the aggregated results of 56 Demographic and Health Surveys[18] in African countries, the ratio is 1.03, albeit with considerable country-to-country variation.[19]
There is controversy whether sex ratios outside the 103-107 range are due to sex-selection, as suggested by some scholars, or due to natural causes. Some scholars argue that strong socioeconomic factors such as the dowry system in India and the one child policy of China are responsible for prenatal sex-selection. In a widely cited article,[20]Amartya Sen supported such views. Other researchers argue that an unbalanced sex ratio should not be automatically held as evidence of prenatal sex-selection; Michel Garenne reports that many African nations have, over decades, witnessed birth sex ratios below 100, that is more girls are born than boys.[21] Angola, Botswana and Namibia have reported birth sex ratios between 94 and 99, which is quite different than the presumed "normal" sex ratio, meaning that significantly more girls have been born in such societies.[22]
In an extensive study, carried out around 2005, of sex ratio at birth in the United States from 1940 over 62 years, statistical evidence suggested the following:[23]
For mothers having their first baby, the total sex ratio at birth was 1.06 overall, with some years at 1.07.For mothers having babies after the first, this ratio consistently decreased with each additional baby from 1.06 towards 1.03.The age of the mother affected the ratio:the overall ratio was 1.05 for mothers aged 25 to 35 at the time of birthmothers who were below the age of 15 or above 40 had babies with a sex ratio ranging between 0.94 and 1.11, and a total sex ratio of 1.04
Factors affecting sex ratiO IN HUMANS
Natural factorS
The natural factors that affect the human sex ratio are an active area of scientific research. Over 1000 articles have been published in various journals. Two of the often cited reviews of scientific studies on human sex ratio are by W. H. James.[24][25] The scientific studies are based on extensive birth and death records in Africa, the Americas, Asia, Australia, and Europe. A few of these studies extend to over 100 years of yearly human sex ratio data for some countries. These studies suggest that the human sex ratio, both at birth and as a population matures, can vary significantly according to a large number of factors, such as paternal age, maternal age, plural birth, birth order, gestation weeks, race, parent's health history, and parent's psychological stress. Remarkably, the trends in human sex ratio are not consistent across countries at a given time, or over time for a given country. In economically developed countries, as well as developing countries, these scientific studies have found that the human sex ratio at birth has historically varied between 0.94 and 1.15 for natural reasons.
In a scientific paper published in 2008,[10] James states that conventional assumptions have been:
there are equal numbers of X and Y chromosomes in mammalian spermX and Y stand equal chance of achieving conceptiontherefore equal number of male and female zygotes are formed, and thattherefore any variation of sex ratio at birth is due to sex selection between conception and birth
The relationship between natural factors and human sex ratio at birth, and with aging, remains an active area of scientific research.
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the sex ratio in humans is approximately 1:1. Due to higher female fetal mortality,[2] the sex ratio at birth worldwide is commonly thought to be 107 boys to 100 girls,[3] although this value is subject to debate in the scientific community. The sex ratio for the entire world population is 102 males to 100 females (2017 est.).[4]Depending upon which definition is used, between 0.1% and 1.7% of live births are intersex.[5][6]
Gender imbalance may arise as a consequence of various factors including natural factors, exposure to pesticides and environmental contaminants,[7][8] war casualties, sex-selective abortions, infanticides, aging, and deliberate gendercide.
Human sex ratios, either at birth or in the population as a whole, are reported in any of four ways: the ratio of males to females, the ratio of females to males, the proportion of males, or the proportion of females.
If there are 108,000 males and 100,000 females the ratio of males to females is 1.080 and the proportion of males is 51.9%. Scientific literature often uses the proportion of males. This article uses the ratio
In the United States, the sex ratios at birth over the period 1970–2002 were 1.05 for the white non-Hispanic population, 1.04 for Mexican Americans, 1.03 for African Americans and Indians, and 1.07 for mothers of Chinese or Filipino ethnicity.[14] Among Western European countries c. 2001, the ratios ranged from 1.04 in Belgium to 1.07 in Switzerland,[15] Italy,[16] Ireland[17] and Portugal. In the aggregated results of 56 Demographic and Health Surveys[18] in African countries, the ratio is 1.03, albeit with considerable country-to-country variation.[19]
There is controversy whether sex ratios outside the 103-107 range are due to sex-selection, as suggested by some scholars, or due to natural causes. Some scholars argue that strong socioeconomic factors such as the dowry system in India and the one child policy of China are responsible for prenatal sex-selection. In a widely cited article,[20]Amartya Sen supported such views. Other researchers argue that an unbalanced sex ratio should not be automatically held as evidence of prenatal sex-selection; Michel Garenne reports that many African nations have, over decades, witnessed birth sex ratios below 100, that is more girls are born than boys.[21] Angola, Botswana and Namibia have reported birth sex ratios between 94 and 99, which is quite different than the presumed "normal" sex ratio, meaning that significantly more girls have been born in such societies.[22]
In an extensive study, carried out around 2005, of sex ratio at birth in the United States from 1940 over 62 years, statistical evidence suggested the following:[23]
For mothers having their first baby, the total sex ratio at birth was 1.06 overall, with some years at 1.07.For mothers having babies after the first, this ratio consistently decreased with each additional baby from 1.06 towards 1.03.The age of the mother affected the ratio:the overall ratio was 1.05 for mothers aged 25 to 35 at the time of birthmothers who were below the age of 15 or above 40 had babies with a sex ratio ranging between 0.94 and 1.11, and a total sex ratio of 1.04
Factors affecting sex ratiO IN HUMANS
Natural factorS
The natural factors that affect the human sex ratio are an active area of scientific research. Over 1000 articles have been published in various journals. Two of the often cited reviews of scientific studies on human sex ratio are by W. H. James.[24][25] The scientific studies are based on extensive birth and death records in Africa, the Americas, Asia, Australia, and Europe. A few of these studies extend to over 100 years of yearly human sex ratio data for some countries. These studies suggest that the human sex ratio, both at birth and as a population matures, can vary significantly according to a large number of factors, such as paternal age, maternal age, plural birth, birth order, gestation weeks, race, parent's health history, and parent's psychological stress. Remarkably, the trends in human sex ratio are not consistent across countries at a given time, or over time for a given country. In economically developed countries, as well as developing countries, these scientific studies have found that the human sex ratio at birth has historically varied between 0.94 and 1.15 for natural reasons.
In a scientific paper published in 2008,[10] James states that conventional assumptions have been:
there are equal numbers of X and Y chromosomes in mammalian spermX and Y stand equal chance of achieving conceptiontherefore equal number of male and female zygotes are formed, and thattherefore any variation of sex ratio at birth is due to sex selection between conception and birth
The relationship between natural factors and human sex ratio at birth, and with aging, remains an active area of scientific research.
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