Question

The average height of humans in industrialized nations has increased steadily for the past 100 years. This trait has clearly changed over time. Most physicians and human geneticists hypothesize that the change is due to better nutrition and a reduced incidence of disease. Has human height evolved? a. Yes, because average height has changed over time. b. No, because changes in height due to nutrition and reduced incidence of disease are not heritable. c. Yes, because height is a heritable trait. d. No, because height is not a heritable trait.

Short answer

b. No, because changes in height due to nutrition and reduced incidence of disease are not heritable.

Step-by-step solution

Determining if height has changed over time.

The exercise states that the average height of humans in industrialized nations has increased steadily for the past 100 years. As average height has changed over time, we can confirm that height does change over time.

Assessing if human height is a heritable trait.

Height is a trait that is influenced by genes, which can be passed down from one generation to the next. Therefore, it is a heritable trait, as it can be inherited from parents to their offspring.

Examining the factors responsible for change in height.

The exercise mentions that most physicians and human geneticists believe that the change in height is due to better nutrition and a reduced incidence of disease. Both of these factors do contribute to height, but they are environmental factors, not genetic factors.

Evaluating the answer choices.

Now, let's assess each answer choice based on the information given and our understanding of evolution: a. Yes, because average height has changed over time. Height has changed over time, but this answer choice does not take into account the importance of whether the change is heritable. b. No, because changes in height due to nutrition and reduced incidence of disease are not heritable. While height is a heritable trait, the changes mentioned in the exercise are due to environmental factors, which are not heritable. This answer choice acknowledges that and can be considered as the correct answer. c. Yes, because height is a heritable trait. Though height is indeed a heritable trait, this answer choice does not address the fact that the changes mentioned in the exercise are due to environmental factors rather than genetic factors. d. No, because height is not a heritable trait. This answer choice is incorrect, as height is a heritable trait. In conclusion, the correct answer is: b. No, because changes in height due to nutrition and reduced incidence of disease are not heritable.

Key concepts

Heritable Traits

Heritable traits are characteristics that can be passed from parents to offspring through genes. These include physical features such as eye color, hair color, and height. The information that dictates these traits is stored in our DNA, and each parent contributes half of the genetic material that makes up a child's complete genetic code.

The importance of heritable traits lies in their ability to provide a link between generations. By analyzing these traits, scientists can study the hereditary patterns and evolution within a species.

• Traits that are not heritable are influenced by environmental factors.
• Heritable traits follow patterns governed by Mendel's laws of inheritance.

Furthermore, understanding heritable traits helps scientists and researchers predict the likelihood of certain traits appearing in the next generation, which is essential for studying human evolution.

Environmental Factors in Evolution

Environmental factors play a significant role in shaping the evolution of species. These are external influences that can affect the growth and development of populations. In the context of human height, better nutrition and improved healthcare systems have been key environmental factors.

These factors can lead to changes in traits that appear within a population, even if they do not directly change the genetic code. For example:

• Access to nutritious food provides the necessary resources for optimal growth, potentially increasing average height.
• Reductions in disease and improved living conditions allow for healthier development during crucial growth periods.

While these elements certainly contribute to the observed changes, they emphasize why such adaptations are not a result of genetic evolution. It's crucial to differentiate between genetic changes and environmentally induced changes, even when these changes affect traits that appear to be evolving.

Genetics and Height

Height is determined by a complex interaction of genetics and environmental factors. Genetically, height is a polygenic trait, meaning it is controlled by multiple genes rather than a single gene. Each of these genes contributes a small amount to an individual's overall height.

While genes provide the blueprint for height, environmental factors such as nutrition and health can significantly influence the final outcome. During a person's growing years, adequate nutrition and health can allow them to reach their potential maximum height. Conversely, poor nutrition or health issues can stunt growth, regardless of genetic predisposition.

The interaction between genetics and environmental factors shows the complexity of predicting outcomes for traits like height. Therefore:

• Genetic influence: Determines potential growth range.
• Environmental influence: Affects actual growth achieved within that range.

This makes height an excellent example of the intricate balance between nature (genetics) and nurture (environmental factors) in human development.