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.
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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.
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In a diverse country like India, where each State is socially, culturally, economically, and politically distinct, measuring Governance becomes increasingly tricky. The Public Affairs Index (PAI 2021) is a scientifically rigorous, data-based framework that measures the quality of governance at the Sub-national level and ranks the States and Union Territories (UTs) of India on a Composite Index (CI).
States are classified into two categories – Large and Small – using population as the criteria.
In PAI 2021, PAC defined three significant pillars that embody Governance – Growth, Equity, and Sustainability. Each of the three Pillars is circumscribed by five governance praxis Themes.
The themes include – Voice and Accountability, Government Effectiveness, Rule of Law, Regulatory Quality and Control of Corruption.
At the bottom of the pyramid, 43 component indicators are mapped to 14 Sustainable Development Goals (SDGs) that are relevant to the States and UTs.
This forms the foundation of the conceptual framework of PAI 2021. The choice of the 43 indicators that go into the calculation of the CI were dictated by the objective of uncovering the complexity and multidimensional character of development governance
The Equity Principle
The Equity Pillar of the PAI 2021 Index analyses the inclusiveness impact at the Sub-national level in the country; inclusiveness in terms of the welfare of a society that depends primarily on establishing that all people feel that they have a say in the governance and are not excluded from the mainstream policy framework.
This requires all individuals and communities, but particularly the most vulnerable, to have an opportunity to improve or maintain their wellbeing. This chapter of PAI 2021 reflects the performance of States and UTs during the pandemic and questions the governance infrastructure in the country, analysing the effectiveness of schemes and the general livelihood of the people in terms of Equity.
Growth and its Discontents
Growth in its multidimensional form encompasses the essence of access to and the availability and optimal utilisation of resources. By resources, PAI 2021 refer to human resources, infrastructure and the budgetary allocations. Capacity building of an economy cannot take place if all the key players of growth do not drive development. The multiplier effects of better health care, improved educational outcomes, increased capital accumulation and lower unemployment levels contribute magnificently in the growth and development of the States.
The Pursuit Of Sustainability
The Sustainability Pillar analyses the access to and usage of resources that has an impact on environment, economy and humankind. The Pillar subsumes two themes and uses seven indicators to measure the effectiveness of government efforts with regards to Sustainability.
The Curious Case Of The Delta
The Delta Analysis presents the results on the State performance on year-on-year improvement. The rankings are measured as the Delta value over the last five to 10 years of data available for 12 Key Development Indicators (KDI). In PAI 2021, 12 indicators across the three Pillars of Equity (five indicators), Growth (five indicators) and Sustainability (two indicators). These KDIs are the outcome indicators crucial to assess Human Development. The Performance in the Delta Analysis is then compared to the Overall PAI 2021 Index.
Key Findings:-
In the Scheme of Things
The Scheme Analysis adds an additional dimension to ranking of the States on their governance. It attempts to complement the Governance Model by trying to understand the developmental activities undertaken by State Governments in the form of schemes. It also tries to understand whether better performance of States in schemes reflect in better governance.
The Centrally Sponsored schemes that were analysed are National Health Mission (NHM), Umbrella Integrated Child Development Services scheme (ICDS), Mahatma Gandh National Rural Employment Guarantee Scheme (MGNREGS), Samagra Shiksha Abhiyan (SmSA) and MidDay Meal Scheme (MDMS).
National Health Mission (NHM)
INTEGRATED CHILD DEVELOPMENT SERVICES (ICDS)
MID- DAY MEAL SCHEME (MDMS)
SAMAGRA SHIKSHA ABHIYAN (SMSA)
MAHATMA GANDHI NATIONAL RURAL EMPLOYMENT GUARANTEE SCHEME (MGNREGS)