Charles Darwin was a careful scientist. In the middle of the 19th century, while he was collecting evidence for his theory that species evolve by natural selection, he noticed it didn’t explain the fancy tails of male peacocks, the antlers paraded by male deer, or why some the males of some species are far larger then their female counterparts.
[wptelegram-join-channel link=”https://t.me/s/upsctree” text=”Join @upsctree on Telegram”]
For these quirks, Darwin proposed a secondary theory: the sexual selection of traits that increase an animal’s chance of securing a mate and reproducing. He carefully distinguished between weapons such as horns, spurs, fangs and sheer size that are used to subdue competing rivals, and ornaments that are aimed at charming the opposite sex.
Darwin thought that sexually selected traits could be explained by uneven sex ratios — when there are more males than females in a population, or vice versa. He reasoned that a male with fewer available females would have to work harder to secure one of them as a mate, and that this competition would drive sexual selection.
In a new study, it is confirmed that there is a link between sexual selection and sex ratios, as Darwin suspected. But surprisingly, the findings suggest Darwin got things the wrong way round. It is found that sexual selection is most pronounced not when potential mates are scarce, but when they’re abundant — and this means looking again at the selection pressures at play in animal populations that feature uneven sex ratios.
Since Darwin’s time, we’ve learned a lot about uneven sex ratios, which are common in wild animal populations. For instance, in many butterflies and mammals, including humans, the number of adult females exceeds the number of adult males.
This skew is most extreme among marsupials. In Australian antechinus, for instance, all males abruptly die after the mating season, so there are times when no adult males are alive and the entire adult population is made up of pregnant females.
In contrast, many birds parade more males than females in their populations. In some plovers, for example, the males outnumber females by six to one.
So why do many birds species have more males, while mammals often have more females? The short answer is that we don’t know. But there are smoking guns.
Explaining uneven sex ratios
Some uneven sex ratios can be partially explained by lifespan differences. Female mammals, including humans, usually outlive their male counterparts by a wide margin. In humans, females live on average about 5 per cent longer than males. In African lions and killer whales, the female lifespan is longer by up to 50 per cent.
Predator preferences could also play a part. African lions kill approximately seven times more male than female buffalo, because male buffalo tend to roam alone, whereas females are protected within herds. In contrast, cheetahs kill many more female Thompson’s gazelles than males, presumably because they can outrun female gazelles easier — especially the pregnant ones.
Finally, males and females often suffer differently from parasites and diseases. The COVID-19 pandemic is a striking example of this: the number of infected men and women is similar in most countries, but male patients have higher odds of death compared to female ones.
Sex ratios and sexual selection
Despite our growing knowledge of uneven sex ratios, Darwin’s insight linking sex ratios with sexual selection has received little attention from scientists. The study sought to address this, pulling together these two strands of evolutionary theory in order to revisit Darwin’s argument.
The study looked in particular at the evolution of large males in different species, which are often several times larger than their female counterparts. It is seen in male baboons, elephant seals and migratory birds, for example. Sometimes, females are larger than males — as with some species of bird, such as the African jacana. The scientific term for when one sex in a species is larger than the other is “sexual size dimorphism”.
It’s clear how sexual selection can sometimes create size dimorphism. Knocking out an enemy requires muscular power, while fight endurance requires stamina. So being bigger often means dominating rivals, thereby winning the evolutionary lottery of reproduction. Analysing 462 different species of reptiles, mammals and birds, the study found a tight association between sexual size dimorphism and sex ratios, vindicating Darwin’s conjectures.
But the trend was the opposite to the one Darwin predicted with his limited evidence. It turns out the most intense sexual selection — indicated by larger males relative to females — occurred in species where there were plenty of females for males to choose from, rather than a scarcity of females as Darwin suggested.
Implications for sexual selection
This in no way invalidates Darwin’s theories of natural selection and sexual selection. The finding simply shows that a different mechanism to the one Darwin proposed is driving mating competition for animals living in sex-skewed populations.
Receive Daily Updates
Recent Posts
Petrol in India is cheaper than in countries like Hong Kong, Germany and the UK but costlier than in China, Brazil, Japan, the US, Russia, Pakistan and Sri Lanka, a Bank of Baroda Economics Research report showed.
Rising fuel prices in India have led to considerable debate on which government, state or central, should be lowering their taxes to keep prices under control.
The rise in fuel prices is mainly due to the global price of crude oil (raw material for making petrol and diesel) going up. Further, a stronger dollar has added to the cost of crude oil.
Amongst comparable countries (per capita wise), prices in India are higher than those in Vietnam, Kenya, Ukraine, Bangladesh, Nepal, Pakistan, Sri Lanka, and Venezuela. Countries that are major oil producers have much lower prices.
In the report, the Philippines has a comparable petrol price but has a per capita income higher than India by over 50 per cent.
Countries which have a lower per capita income like Kenya, Bangladesh, Nepal, Pakistan, and Venezuela have much lower prices of petrol and hence are impacted less than India.
“Therefore there is still a strong case for the government to consider lowering the taxes on fuel to protect the interest of the people,” the report argued.
India is the world’s third-biggest oil consuming and importing nation. It imports 85 per cent of its oil needs and so prices retail fuel at import parity rates.
With the global surge in energy prices, the cost of producing petrol, diesel and other petroleum products also went up for oil companies in India.
They raised petrol and diesel prices by Rs 10 a litre in just over a fortnight beginning March 22 but hit a pause button soon after as the move faced criticism and the opposition parties asked the government to cut taxes instead.
India imports most of its oil from a group of countries called the ‘OPEC +’ (i.e, Iran, Iraq, Saudi Arabia, Venezuela, Kuwait, United Arab Emirates, Russia, etc), which produces 40% of the world’s crude oil.
As they have the power to dictate fuel supply and prices, their decision of limiting the global supply reduces supply in India, thus raising prices
The government charges about 167% tax (excise) on petrol and 129% on diesel as compared to US (20%), UK (62%), Italy and Germany (65%).
The abominable excise duty is 2/3rd of the cost, and the base price, dealer commission and freight form the rest.
Here is an approximate break-up (in Rs):
a)Base Price | 39 |
b)Freight | 0.34 |
c) Price Charged to Dealers = (a+b) | 39.34 |
d) Excise Duty | 40.17 |
e) Dealer Commission | 4.68 |
f) VAT | 25.35 |
g) Retail Selling Price | 109.54 |
Looked closely, much of the cost of petrol and diesel is due to higher tax rate by govt, specifically excise duty.
So the question is why government is not reducing the prices ?
India, being a developing country, it does require gigantic amount of funding for its infrastructure projects as well as welfare schemes.
However, we as a society is yet to be tax-compliant. Many people evade the direct tax and that’s the reason why govt’s hands are tied. Govt. needs the money to fund various programs and at the same time it is not generating enough revenue from direct taxes.
That’s the reason why, govt is bumping up its revenue through higher indirect taxes such as GST or excise duty as in the case of petrol and diesel.
Direct taxes are progressive as it taxes according to an individuals’ income however indirect tax such as excise duty or GST are regressive in the sense that the poorest of the poor and richest of the rich have to pay the same amount.
Does not matter, if you are an auto-driver or owner of a Mercedes, end of the day both pay the same price for petrol/diesel-that’s why it is regressive in nature.
But unlike direct tax where tax evasion is rampant, indirect tax can not be evaded due to their very nature and as long as huge no of Indians keep evading direct taxes, indirect tax such as excise duty will be difficult for the govt to reduce, because it may reduce the revenue and hamper may programs of the govt.