The mystery of why most mammals, including humans, have five fingers has interested scientists for decades. Despite the enormous diversity of mammalian species, from cats to kangaroos, the basic pattern of five digits is extremely stable. But what causes this evolutionary convergence toward quintality? Thomas Stewart, an evolutionary biologist at Penn State, offers insight into the underlying mechanisms behind this fascinating event. He explains, “There is some variation… However, scientists have discovered that these animals start out with as many as five fingers as embryos, but they shrink away before they are born.” Genetic guidance: how Hox genes regulate digit development Hox genes are crucial to this developmental process because they orchestrate the production of digits throughout embryonic development. Stewart elucidates, “Hox genes encode proteins that help regulate the activity of other genes, turning them on or off… They help ensure that body parts end up in their correct location.” Working in conjunction with the sonic hedgehog gene, they orchestrate the growth of finger buds, which may either continue developing or regress, leading to the formation of distinct digits. The sonic hedgehog gene—yes, it’s really called that—plays a pivotal role in limb development. It produces signaling proteins that guide the organization of tissues during embryonic growth. In the context of finger formation, the sonic hedgehog gene controls the patterning of cells, influencing whether they proliferate to form fingers or undergo apoptosis, a process where cells die, resulting in the separation of digits. Stewart acknowledges that the process is complex, with variations depending on the species. This suggests a common ancestral origin for the trait, known as “homology,” where organisms inherit similar structures from their forebears. Thus, the prevalence of the five-finger pattern among tetrapods underscores its evolutionary significance. During embryogenesis, finger buds arise via a complex interplay of genetic communication, paving the way for the production of different fingers. Stewart emphasizes the delicate nature of this process, stating, “Exactly how this happens is admittedly a pretty complicated problem.” Tracing back through time: unraveling the origins of the five-finger plan The evolution of the iconic five-finger design dates back millions of years to the emergence of tetrapod animals. Stewart explains, “The first known species to generate fingers developed from fish some 360 million years ago, and they had up to eight digits… The common ancestor of all living tetrapods must have somehow evolved to have five fingers.” This concept of homology implies a shared heritage among tetrapods, with the five-finger pattern emerging as an evolutionarily conserved characteristic passed down via consecutive generations. The enigma of evolution: debating the purpose of the quintessential pattern While the genetic underpinnings of five fingers provide insights into their developmental origins, determining the evolutionary reason for this common characteristic is a daunting challenge. Kimberly Cooper, an evolutionary developmental geneticist at the University of California, San Diego, criticizes the popular notion of canalization, which holds that features persist throughout time due to evolutionary advantages. Cooper uses the occurrence of polydactyly, or extra fingers, as a counter-argument, implying that mutations altering the fundamental pattern can occur. As scientists grapple with the complexities of evolutionary biology, Stewart emphasizes the allure of this enduring mystery, stating, “We can ask a very simple question of why don’t we see more than five fingers, and it seems like we should arrive at a simple answer… But it’s a really deep problem.” In the ever-changing landscape of scientific research, the effort to fathom the mysteries of mammalian evolution continues to pique interest and fuel groundbreaking discoveries.  The post Why do most mammals have five fingers? first appeared on The Optimist Daily: Making Solutions the News.

Renewable energy surpassed 30 percent of the global electricity supply for the first time, marking a milestone in the planet’s energy shift. This spike in clean electricity, mostly from wind and solar power, represents a watershed point in the move to sustainable energy options. The ongoing renewable revolution According to a report by climate ThinkTank Ember, renewables have grown exponentially, from 19 percent of global electricity in 2000 to more than 30 percent last year. Dave Jones, Ember’s head of global analytics, underscores the revolutionary nature of this move, saying, “The renewables future has arrived.” Solar power shines brilliantly Solar energy emerges as the MVP in this green revolution, exceeding coal as the dominant driver of electricity growth in 2023. Ember’s study focuses on the remarkable expansion of solar power, which has been the fastest-growing source of electricity for the 19th straight year. The global perspective: a comprehensive review of electricity data The comprehensive assessment of global power data includes 80 countries, which account for 92 percent of worldwide electricity demand, and provides insights into the global energy picture. This statistic demonstrates the extensive use of renewable energy solutions across many geographies. Driving down fossil fuel generation The growth of clean power has dramatically slowed the use of fossil fuels, with Ember reporting an almost two-thirds decline in fossil fuel generation over the last decade. This trend is forecast to continue, with a two percent decline in worldwide fossil fuel generation predicted for the coming year. Peak emissions in the power sector Jones underlines the historical significance of 2023 as a watershed event in the energy transition, with peak emissions in the power sector. While the reduction of power sector emissions is unavoidable, the rate of this transition is dependent on the ongoing expansion of renewable energy initiatives. Despite great advancements in renewable energy adoption, fossil fuels remain heavily used in a variety of industries, including transportation, heavy manufacturing, and heating. Addressing these difficulties needs coordinated efforts to expedite the transition to cleaner energy sources. Charting the path forward: The UN’s ambitious targets World leaders have set lofty goals for renewable energy, intending to generate 60 percent of global electricity from renewable sources by 2030. This ambitious objective agreed upon during the UN’s COP28 climate change summit demonstrates the global commitment to tackling climate change through renewable energy adoption. Welcoming the future of sustainable energy The emergence of renewable energy represents a watershed point in the fight against climate change and the transition to a sustainable energy future. As countries step up their efforts to adopt clean energy solutions, the globe is ready to usher in a new era of environmental stewardship and energy resiliency.The post The rise of renewable energy: a tipping point in global electricity sources  first appeared on The Optimist Daily: Making Solutions the News.

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