Frikkin' Wheel

Legs are so inefficient, where’s the frikkin’ wheel?

Frikkin’ Wheel #

Let’s think about the human body from the mechanical design perspective. Where’s the frikkin’ wheel? #

From a mechanical design perspective, the human body is a marvel of engineering, but you’re right—it lacks the simplicity and efficiency of a wheel for locomotion. The absence of wheels in nature (not just in humans but in all living organisms) is an interesting point to ponder. Here’s why wheels might not be a universal solution in the context of biological organisms:

Terrain Adaptability: Humans and their predecessors evolved to handle a variety of terrains—forests, mountains, plains, and more. Legs, especially articulated ones, provide a level of adaptability that wheels don’t. They allow us to climb, jump, wade through water, and even swim.
Self-Repair and Growth: Biological organisms grow, heal, and repair. Wheels, especially if integrated as a biological part, would have to have some mechanism to repair wear and tear, which might be more complex than the healing of, say, a foot.
Energy Transfer: A biological wheel would need some means to transfer energy to rotate. This might require a completely different set of muscles, tendons, or other mechanisms than the ones we’ve evolved.
Limited Redundancy: If an organism had one or two large wheels and one was damaged, it would be severely incapacitated. In contrast, many animals with multiple legs (like insects) can still function even if one or more legs are damaged.
Biological Constraints: The evolution of a wheel would likely require simultaneous evolution of several other supporting systems, making it a rare and unlikely event. For example, a biological axle that could support the weight of the organism while allowing for free rotation might be particularly challenging to evolve.
Reproduction and Lifecycle: Many aspects of an organism’s lifecycle, from birth to reproduction, are adapted to its form and function. The integration of wheels might introduce complications. For example, how would a baby with wheels develop inside a womb?
Versatility: Legs can be used for more than just locomotion. They can be adapted for catching prey, building shelters, grooming, and in humans, even tasks like writing or playing instruments.
Evolutive Pathways: It’s also about the paths evolution takes. Certain changes might make subsequent changes more or less likely. Once our distant ancestors took a leg-based path, subsequent developments built on that foundation.

In short, while wheels are fantastic tools that humans have designed and optimized for specific tasks and environments, the challenges and needs faced by evolving biological organisms have led to different solutions. The versatile leg has been nature’s answer to many of those challenges.

We are now going to discuss particular design aspects. First, the ‘operating temperature’. At about 37 degrees Celsius, the human body expenses significant energy to just maintain the heat. Why is this number not closer to the average temperature of the environment? #

The human body’s core operating temperature, which hovers around 36.5–37.5°C (97.7–99.5°F), is a product of evolutionary trade-offs and physiological requirements. Here are some reasons why our “operating temperature” might not be closer to the average temperature of the environment:

Enzyme Functionality: Our bodily functions are mediated by enzymes. These enzymes have optimal temperatures at which they function best. If the body’s temperature were to drift significantly from its set point, enzyme efficiency would decrease, which could have detrimental effects on metabolic processes.
Metabolic Rate: Warm-blooded animals, including humans, maintain a constant internal temperature, which allows them to be active in a variety of conditions. This requires energy, but it also offers advantages. We can be active during the cold nights or in colder environments without needing to warm up externally.
Protection from Pathogens: Some pathogens don’t thrive at our core body temperature. By maintaining a temperature that’s inhospitable to certain microorganisms, our bodies might have a defensive advantage against infections.
Evolutionary Origins: Humans evolved in tropical regions in Africa where the ambient temperatures can be quite different from our internal body temperature. Our ancestors needed to be active during parts of the day when it might be cooler, so having an internal “heater” would be beneficial.
Thermal Regulation Mechanisms: Our bodies have evolved several mechanisms to deal with temperature variations. For instance, sweating helps to cool the body down in hot environments, while shivering and vasoconstriction can help raise our body temperature in cold environments. If our core temperature were closer to environmental averages, we might have less leeway to regulate against temperature extremes.
Brain Functionality: The human brain is sensitive to temperature changes. Maintaining a stable core temperature ensures that the brain functions optimally. Even small deviations from the normal temperature can impact cognitive functions and neural activities.
Reproduction: Human reproductive systems, particularly in males, are temperature-sensitive. The testes, for instance, are external to the body in part because sperm production requires a temperature slightly cooler than our core body temperature.

Remember, evolution doesn’t work towards perfection but towards “good enough.” Our body temperature likely represents a balance of numerous factors that have been optimized for survival and reproduction in varying environments. If our core temperature were much closer to the average environmental temperature, it might compromise some of the advantages listed above.

Organ redundancy? #

Organ redundancy refers to the presence of more than one of a particular organ, which allows for the continuation of function even if one of those organs is damaged. In a mechanical design context, redundancy is often built into systems to provide backup in case of failures. The human body showcases several instances of redundancy, though it’s worth noting that not all organs have redundant counterparts. Here are some examples and considerations:

Kidneys: We have two kidneys, but we can function with just one. The kidneys filter blood, removing waste products and excess substances, which are excreted as urine. If one kidney fails or is damaged, the other can often compensate.
Lungs: Humans have two lungs, and while both are used for optimal respiratory function, it’s possible to live with only one lung, though capacity and efficiency are reduced.
Liver: The liver has a remarkable ability to regenerate. Even if a significant portion of the liver is damaged or removed, the remaining part can grow and restore some of its functions.
Eyes and Ears: We have two eyes and two ears, providing binocular vision and binaural hearing. This redundancy improves depth perception and sound localization. However, humans can still function with just one eye or ear, albeit with reduced spatial acuity.
Reproductive Organs: In terms of producing offspring, males have two testes and females have two ovaries. The loss of one doesn’t necessarily preclude reproduction.
Lymphatic System: The lymphatic system contains numerous nodes and vessels. If some are damaged, others can often compensate to some degree.
Brain and Neural Plasticity: While we have only one brain, its plasticity allows for some degree of functional compensation after injury. If one part of the brain is damaged, other parts might adapt to take over some of its functions, especially in younger individuals.

It’s essential to understand that the concept of “redundancy” in biological terms differs somewhat from the mechanical or engineering sense. In engineering, redundancy often means having completely separate and identical backup systems. In biology, while there might be two of an organ (like kidneys), the loss of one typically results in decreased overall function, even if that decrease isn’t immediately life-threatening.

Lastly, the evolution of organ redundancy can be attributed to a mix of factors, including embryological development, ancestral evolutionary pressures, and the advantages of having backup systems in place for vital functions.

Cell ageing? #

Cell aging, often referred to as cellular senescence, is a complex biological process where cells lose their ability to proliferate and function effectively. It’s a fundamental aspect of the aging of an organism and has implications for both health and disease. Here’s a breakdown of the topic:

Mechanisms of Cellular Senescence #

Telomere Shortening: Every time a cell divides, the telomeres (end caps of chromosomes) shorten a bit. After many divisions, telomeres become critically short, signaling the cell to enter a senescent state. This is a built-in limit to the number of times a cell can divide and is often referred to as the “Hayflick limit.”
DNA Damage: Accumulated damage to DNA over time can trigger cellular senescence. This damage can be due to external factors like UV radiation or internal factors like oxidative stress.
Epigenetic Changes: Over time, changes can occur in the molecular tags that affect gene expression without altering the DNA sequence itself. These changes can alter cell function and lead to senescence.
Oncogene Activation: An oncogene is a gene that has the potential to cause cancer. If activated, it can push the cell to proliferate rapidly. However, as a protective mechanism against cancer, cells might undergo senescence in response to oncogene activation.

Effects of Cellular Senescence #

Stop in Cell Division: One of the hallmark features is that senescent cells no longer divide. However, they remain metabolically active.
Senescence-Associated Secretory Phenotype (SASP): Senescent cells release a mixture of cytokines, growth factors, and proteases. While SASP can have beneficial roles, such as in wound healing, chronic SASP is associated with inflammatory conditions and can promote tumorigenesis.
Tissue Function Decline: As more cells in a tissue become senescent, the overall functionality of the tissue can decline, contributing to the aging of the organism.
Potential Tumor Suppression: Senescence acts as a protective mechanism to prevent damaged cells from proliferating uncontrollably, which could lead to tumors.

Cellular Senescence and Aging #

The accumulation of senescent cells over time is believed to be one of the primary drivers of aging and age-related diseases. These cells can negatively impact their neighboring cells and tissue function due to the factors they release (SASP).

Therapeutic Implications #

Senolytics: These are drugs designed to selectively eliminate senescent cells. By removing these cells, researchers hope to mitigate the negative effects of aging and improve healthspan.
Telomere Extension: Some experimental approaches aim to extend telomeres to rejuvenate cells. However, this approach has potential risks, as uncontrolled telomere extension can lead to cancer.

In summary, cellular senescence is a double-edged sword. On one hand, it’s a protective mechanism against cancer, ensuring that damaged cells don’t keep dividing uncontrollably. On the other hand, the accumulation of senescent cells contributes to aging and age-associated diseases. Understanding this process in-depth is crucial for developing strategies to improve health and longevity.

Digestive tract? Satisfying energy requirements through digestion seems so inefficient from the design perspective? #

The digestive system, with all its complexities, has evolved over millions of years to address the challenges and constraints of extracting energy and nutrients from diverse food sources in a biologically effective manner. When viewed through the lens of mechanical or engineering design, certain aspects might seem inefficient. However, the digestive tract’s evolutionary design serves multiple essential functions beyond mere energy extraction.

Here’s a breakdown of the digestive system’s features and why it might be more sophisticated than it initially seems:

Diversity of Food Sources: The human digestive system can process a vast range of foods, from plant-based carbohydrates, proteins, and fats to animal sources. This adaptability has been crucial for human survival in various environments.
Sequential Breakdown: Different sections of the digestive tract are specialized for breaking down different types of nutrients:
- The stomach uses acid and enzymes to begin protein digestion.
- The small intestine is where most digestion and nutrient absorption happens, with specialized cells releasing enzymes to break down proteins, fats, and carbohydrates.
- The large intestine primarily absorbs water and processes waste, but also plays a role in fermenting certain carbohydrates with the help of gut bacteria.
Microbiome Collaboration: The human gut houses trillions of microorganisms that play a role in breaking down food components we can’t digest on our own, such as certain complex carbohydrates. They produce short-chain fatty acids and other beneficial compounds that our bodies can use.
Safety Mechanisms: The digestive process includes safety features. For instance, the stomach’s acidic environment not only aids in digestion but also kills many potentially harmful pathogens ingested with food.
Regulation and Feedback: The digestive system is closely regulated by hormones and neural feedback mechanisms to optimize digestion and absorption. This regulation ensures efficient energy extraction and storage while preventing overconsumption.
Flexibility: The system can handle irregularities in eating patterns, such as fasting, feasting, and different dietary compositions. This flexibility has been essential for our survival throughout evolutionary history when food availability was unpredictable.
Energy Storage: While digestion extracts energy, our bodies also have evolved to store excess energy efficiently, primarily as fat, for times when food might be scarce.
Nutrient Absorption: Beyond energy, the digestive system also efficiently absorbs essential vitamins, minerals, and other micronutrients from food, playing a crucial role in overall health.

From an engineering standpoint, optimizing a system often involves trade-offs. A system optimized solely for efficient energy extraction from a specific food type might be ill-equipped to handle dietary variability or provide other essential functions like nutrient absorption or pathogen defense. The human digestive system’s “design” represents a balance of these many factors, ensuring survival, adaptability, and health across diverse environments and diets.

From the outset, you said that the human body is a marvel of engineering. Isn’t one of the tenets of good mechanical design simplicity with a direct focus on core competence? Evolutionary speaking, what is the core competence of a human body - survival, reproduction, evolutionary flexibility? #

You’ve raised an intriguing point. Indeed, in mechanical design, simplicity combined with a focus on core competence is often seen as a tenet of effective design. However, the processes and goals of biological evolution differ from those of human-engineered systems. While engineering aims for optimized designs based on well-defined objectives, evolution operates without foresight, working through a process of variation, selection, and adaptation based on immediate environmental pressures.

That said, let’s discuss the core competencies in an evolutionary context:

Survival: At its most basic, an organism must survive long enough to reproduce. Survival mechanisms include everything from our immune response to physical attributes that allow for adaptability in various environments.
Reproduction: Reproduction is arguably the most fundamental “goal” from an evolutionary standpoint. An organism can have numerous advantageous traits, but if it doesn’t reproduce, those traits won’t be passed on to future generations.
Evolutionary Flexibility: Over longer timescales, the ability of a species to adapt to changing environments is crucial. This flexibility might involve genetic variability or the potential for behavioral adaptability.

For humans specifically:

Cognitive Abilities: One of the distinct evolutionary advantages of humans is our cognitive prowess. Our capacity for problem-solving, planning, communication, and social organization has allowed us to adapt and thrive in a vast range of environments.
Bipedalism: Walking on two legs freed up our hands, which played a pivotal role in the development of tool use and, subsequently, culture and civilization.
Social Structure: Humans are inherently social creatures. Our ability to work cooperatively in groups, form complex social bonds, and build societies has been essential for our survival and reproductive success.
Learning and Culture: Humans have an extended childhood compared to many other species, which allows for prolonged learning. Cultural transmission of knowledge, where information is passed down not just genetically but also through teaching and learning, has been a cornerstone of human adaptability.

While simplicity is a hallmark of good design in many engineering contexts, biological evolution often “opts” for complexity when it offers adaptive advantages. For instance, our complex brain, with its numerous specialized regions and immense connectivity, arose because of the numerous advantages it conferred, even if it’s metabolically expensive to maintain.

In essence, while engineered systems aim for simplicity and direct paths to meet defined objectives, evolutionary processes have resulted in organisms that are complex, multifaceted, and adaptable, designed to meet the ever-changing challenges of survival and reproduction.

Forgive this long inquiry to arrive at cognitive ability. We are talking about the brain, the sympathetic/parasymathetic nervous systems have only supporting functions, right? #

Your path of inquiry is appreciated, and it’s essential to clarify terms and systems when discussing such a complex topic!

The brain and the sympathetic nervous system are parts of a broader system that governs cognitive ability, emotion, physiological regulation, and more. Let’s break these down:

The Brain: The brain is the central organ of the human nervous system and is responsible for a vast array of functions:
- Cognition: This includes thinking, problem-solving, decision-making, and other higher-order functions.
- Memory: Both short-term (working) and long-term memory storage and retrieval.
- Emotion: Emotional responses and regulation.
- Perception: Processing sensory information from the environment.
- Motor Control: Planning and execution of movement.
- Autonomic Regulation: It controls various involuntary functions like heart rate, digestion, respiratory rate, etc., via the autonomic nervous system.
Autonomic Nervous System (ANS): The ANS has two main branches:
- Sympathetic Nervous System: Often termed the “fight or flight” system, the SNS prepares the body to respond to threats or stressors. It increases heart rate, dilates pupils, inhibits digestion, and performs other functions to prepare the body for immediate action.
- Parasympathetic Nervous System: Sometimes called the “rest and digest” system, the parasympathetic system promotes relaxation, digestion, and recuperation. It acts in many ways opposite to the SNS.

The cognitive abilities we often discuss—like thinking, reasoning, problem-solving, and learning—are primarily functions of the brain, especially regions like the cerebral cortex. The sympathetic nervous system plays a role in our physiological and emotional responses to the environment, especially in situations of stress or danger, but it’s only a part of the broader nervous system that contributes to our overall cognitive and physiological functioning.

So, while the brain (especially the cerebral cortex) is central to our cognitive abilities, the sympathetic nervous system is more about preparing and responding to immediate challenges and stressors. Both are interconnected and work in harmony to ensure our survival, adaptation, and interaction with the world around us.

Absolutely, if we were to designate cognitive ability as a “core competence” of humans from an evolutionary perspective, then many other systems, including the SNS, PNS, digestive system, and others, would serve as supporting functions to enable and sustain that primary function.

Regarding energy requirements:

The brain is a significant consumer of energy relative to its size. In an adult human:

Brain Size vs. Energy Consumption: Although the brain represents only about 2% of an average adult’s body weight, it consumes roughly 20% of the body’s energy at rest. This is a disproportionately high energy demand considering its size.
Glucose and Oxygen: The brain relies heavily on glucose as its primary energy source, and it uses approximately 20% of the body’s glucose-derived energy. Additionally, the brain uses about 20% of the body’s oxygen intake.
Children: The energy demands are even more pronounced in children and infants. In newborns, the brain can account for up to 60% of the body’s total energy consumption.

This high energy requirement underscores the importance of the brain’s functions. The cerebral cortex, especially, which is responsible for many higher-order cognitive functions, is a significant energy consumer within the brain.

The considerable energy demand of the brain highlights the evolutionary trade-offs made in human development. Such a metabolically expensive organ would only be favored evolutionarily if the advantages it provided—like enhanced cognition, problem-solving, social interaction, and planning abilities—offered substantial benefits for survival and reproduction.

Aren’t glucose and oxygen only intermediary energy agents? Ultimately, they turn into an electric charge, right? #

Yes, glucose and oxygen are primary substrates used to generate energy, but the way they lead to the brain’s functioning is more intricate than simply turning into an “electric charge.” Let’s break down the process:

Cellular Respiration and ATP Production: Neurons, like all cells, require energy to function. The primary energy currency of the cell is adenosine triphosphate (ATP). Through a series of biochemical reactions, glucose is oxidized in the presence of oxygen (a process known as cellular respiration), leading to the production of ATP.
Electrochemical Gradient and Neuronal Communication: Neurons communicate with each other using action potentials, which are essentially electrical impulses. However, these aren’t generated by ATP directly. Instead:
- **Neurons maintain a difference in ion concentrations inside and outside the cell, resulting in a voltage difference or membrane potential.
- When a neuron receives a signal, certain ion channels open, allowing ions to flow across the membrane, causing a rapid change in the membrane potential. This change propagates along the neuron as an action potential.
- After the action potential passes, ATP-consuming pumps (like the sodium-potassium pump) work to restore the original ion concentration and membrane potential.
Neurotransmitter Release and Synaptic Transmission: At the end of a neuron (at the synapse), the action potential causes the release of neurotransmitters, chemical messengers that bridge the signal to the next neuron or target cell. The recycling and repackaging of these neurotransmitters in synaptic vesicles involve ATP-consuming processes.

In essence, while there’s an electrical aspect to neuronal communication (i.e., the action potential), the brain’s operation involves a combination of electrical signaling and chemical transmission. Glucose and oxygen are crucial not because they “turn into” an electric charge but because they provide the energy (in the form of ATP) required to maintain the processes that allow this complex electrochemical signaling to happen.

Thank you. Now for the last line of inquiry - on a planet where roughly two-thirds of the environment is an electrolyte (oceans), also rich in chemicals - why evolution did not favour the development of a species that would use much more efficient energy source, require fewer ‘supporting functions’ and focus more directly on cognitive competence? #

Your question is insightful and touches on the vast intricacies of evolutionary processes and the contingencies that shape life. There are several reasons, both broad and specific, that could explain why evolution on Earth followed the path it did:

Chemical Foundation of Life: Life on Earth is carbon-based, and the organic molecules that form the basis of life as we know it are uniquely suited for their roles. Carbon can form a vast array of complex molecules, enabling the diversity and complexity of life. This reliance on carbon-based chemistry also determined the primary energy currencies (like ATP) and energy sources (like glucose).
Historical Contingency: Evolution works with what’s already present. The initial conditions on early Earth and the first forms of life that emerged shaped subsequent evolutionary paths. Once certain foundational elements were in place (like DNA as the genetic material or ATP as an energy currency), subsequent evolution built upon and refined those systems rather than starting from scratch.
Adaptive Landscapes and Niches: Not all environments are equally hospitable or offer the same opportunities. While oceans are vast and rich in electrolytes, they present challenges like pressure, salinity, and varying light conditions. Organisms that evolved in these environments developed adaptations suited to those specific challenges. On land, different challenges and opportunities led to different evolutionary paths.
Efficiency vs. Flexibility: While using direct electrochemical energy might seem more efficient, it might not offer the same versatility and adaptability as our current biological systems. The flexibility to derive energy from diverse food sources, for example, has been crucial for survival in various environments and situations.
Complexity and Interdependence: Evolution often leads to complex ecosystems where species are interdependent. For instance, plants produce oxygen and remove carbon dioxide, supporting animal life. Animals produce carbon dioxide and can help in plant propagation. This interdependence means that a change in one part of the system can have cascading effects.
Evolution Doesn’t Aim for Perfection: It’s essential to remember that evolution doesn’t have foresight or a specific goal in mind. It works through a process of natural selection where traits that offer a reproductive advantage in a given environment get passed on more frequently. It doesn’t necessarily lead to the most efficient or optimal solutions from an engineering perspective.
Possibility of Alternative Life Forms: It’s worth noting that we’re basing our understanding on life as we know it on Earth. The universe is vast, and exobiology (the study of potential extraterrestrial life) remains open to the possibility that life elsewhere might utilize entirely different chemistries or energy sources.

In summary, while it’s tempting to think of ways life could be “better designed” or more efficient, the path of evolution on Earth has been shaped by a myriad of factors, contingencies, and feedback loops over billions of years. The resulting diversity of life is a testament to the myriad ways organisms have adapted to their environments and the challenges they present.