Modern World


Are Humans Still Evolving?

  • Evolutionary Future of Our Species

    • Examining changes in evolutionary pressures affecting humans:

    • Environment

    • Diet

    • Lifestyle

    • Disease

  • Examples of “Recent” Change

    • Lactase persistence (ability to digest lactose into adulthood)

    • Variation in skin pigmentation in response to UV exposure

Reduced Selection? Or Changes in Selection?

  • The idea that some selection pressures have eased due to:

    • Advances in technology

    • Development of modern medicine

  • Humans create comfortable microenvironments that provide different living conditions.

  • This may allow for the passing down of alleles that would have been deleterious in the past but are less harmful or not harmful in the current environment.

Specific Examples of Evolutionary Changes

Myopia

  • Definition: Reduced ability to see in focus at long distances; commonly referred to as "nearsightedness".

  • Visual acuity was more crucial for survival in evolutionary history.

  • Today, myopia can be easily corrected with glasses or contact lenses.

  • Question remains: Is there any ongoing selective pressure regarding myopia?

Dental Caries

  • Definition: Dental cavities caused by environmental and genetic risks.

  • Historically, severe periodontal disease and caries could lead to increased mortality risk or death.

  • Current implications: Untreated dental caries are associated with poor health outcomes and are confounded with socioeconomic status (SES) and other factors.

PKU

  • Definition: Phenylketonuria, an inherited metabolic disorder caused by several allele variants.

  • Characteristic: Individuals with PKU lack the enzyme needed to break down phenylalanine.

  • Danger: If phenylalanine accumulates in the body, it can be dangerous and requires dietary management to prevent severe intellectual impairment.

  • Impact: Since the 1960s, widespread testing of infants has been established to detect PKU early.

Type I Diabetes

  • Also known as juvenile diabetes.

  • Observations: The incidence of Type I diabetes has been increasing in recent years.

  • Factors: Availability of modern medical treatments has relaxed previous selective pressures on Type I diabetics, who typically did not survive long in earlier conditions.

  • Mechanism: Gene-environment interaction; it involves an autoimmune response where the immune system attacks insulin-producing cells in the pancreas, leading to a complete inability to produce insulin, necessitating lifelong insulin supplementation for survival.

Climate and Evolution: Are We Evolved to Be Adaptable?

Stress

  • Definition: Stress responses are crucial for survival, traditionally categorized under “fight or flight.”

  • Health Implications: Elevated or chronic stress is associated with negative health outcomes including:

    • Cardiovascular diseases

    • Accelerated aging

  • Socioeconomic Inequality: Stress is identified as one of the sources of health disparities across populations.

Obesity

  • Description: Considered a form of malnutrition.

  • Concepts:

    • Thrifty Phenotype: Suggests that certain genetic adaptations permit better fat storage in environments with unreliable food sources.

    • Thrifty Genotype: Proposes that individuals with gene variants that enhance survival during periods of food scarcity are naturally selected for.

  • Food Insecurity: The relationship between food access and obesity rates.

  • Statistics on Obesity:

    • Obesity is defined using the Body Mass Index (BMI), where:

    • extBMI=Weight (kg)Height (m)2ext{BMI} = \frac{\text{Weight (kg)}}{\text{Height (m)}^2}

    • Obesity: BMI ≥ 30.

    • Data indicates an increase in obesity rates among adults from 1975 to 2016.

    • Graph data points reflecting obesity prevalence:

    • 2016: 35% of adults from the dataset were classified as obese.

  • Metabolic Diseases: Noted as correlated with obesity rates and health complications.

Culture and Evolution

  • Overview: Culture influences selective pressures through:

    • Food production methods

    • Clothing adaptations

    • Housing developments

    • Technological advancements

    • Education dissemination

    • Medical practices

  • Future Considerations: Speculation on how culture will continue to influence future generations of humans.

Understanding Human Variation

  • Discussion Points:

    • Humans generally exhibit low genetic variability as a species.

    • The role of evolutionary forces throughout human history.

    • Adaptations to local conditions occur but are not guaranteed outcomes.

    • Concept of Race: Race does not sufficiently describe human biological variation.

    • Emphasis on complex interactions between biological variation, cultural variation, and environmental factors.