Let there be light*

Enlightenment

 

*Light herein is taken to mean all forms of radiation of the electromagnetic (EM) spectrum from gamma rays to radio waves. (http://upload.wikimedia.org/wikipedia/commons/c/cf/EM_Spectrum_Properties_edit.svg)

Light is not only our medium of contact with the world; in a very real sense, it is the basis of our existence. Lee Smolin – The life of the cosmos.

Not so silent a night

In the beginning there was darkness (or maybe wavelengths beyond our current ability to access). In that darkness symmetry was broken and a quark soup developed, the quarks were then confined to be near each other. They began making protons and neutrons. At a temperature of around 4000K matter was free flowing with electrons streaming away on their own like a river– a state of matter called plasma. Matter in this state interacted freely with photons exchanging energy. A photon (fundamental unit of any electromagnetic radiation) could not move very far without bumping into matter and hence could not travel far. The universe was opaque.

First light

Then the universe cooled to below 3000K. Electrons began to come to sit around nuclei (protons with their neutrons) to form stable atoms forming mainly hydrogen gas and little bit of helium. The photons were freed from their interaction with matter; they could now roam the universe. The initial EM radiation was mainly in the form of gamma radiation (high energy, short wavelength) but during its 14 billion year long journey it lost its energy and has a wavelength of microwaves today. Hence we perceive this light (which is there in every direction of the universe) as microwaves.

The earliest light we can see (albeit with the most sophisticated instruments at our disposable like COBE, WMAP and Planck) is this microwave background radiation. This dates to about 380,000 years after the Big Bang.

All that we know (all the information) about everything around us comes to us as EM radiation. No light no information. We can access our immediate world and the universe at large only through light.

First life by light?

Photocatalysis  (by UV) of simple organic compounds to more complex ones is a frontrunner for the method in which life was kickstarted on the planet see blog on abiogenesis.https://paulramesh.wordpress.com/?s=abiogenesis

First sight

Newton spent a huge effort (including prodding his eye with needles) trying to understand it. Charles Darwin wondered how natural selection might have produced it. The mechanism of vision has been a preoccupation of the best scientific minds.  Why do we only see what we see? Or why is the visible part of the EM spectrum visible? How do we see what we see?

Why do we see only what we see?

variegated flutterer courtesy jay

If you have wondered why only the visible part of the spectrum is accessible to our eyes. It has to do with physics, chemistry and (evolutionary) biology ,

About 20% of stars have a temperature of 6000K. The light emitted at this temperature falls a little to each side of the visible spectrum (400-700nm). The denizens of any planet would do well to adapt to access this wavelength over others. EM radiation that has high energy ionizes and changes destructively the chemicals they meet. EM radiation with low energy interact weakly or not at all and does not cause much change. The wavelengths of light most likely to interact with chemicals imparting energy to them and not ionizing them in the process are in the near visible spectrum. This interaction enables the light energy to be converted to chemical energy and an electrical impulse that the brain can perceive as a signal.

Eyes appear by and far to have evolved first in an aquatic environment. Only green and blue wavelengths penetrate water to any extent. This may be another reason why we can see only what we can see.

In an alien world with a star streaming a different wavelength may lead to eyes that see differently. The planet Krypton may well have had its parent star stream X-rays that could explain Superman’s X-ray vision.

How do we see what we see?

A photon hits your eye and goes through virtually all layers of the eye – reaches the retina where the photoreceptor cells (rods, cones) are located. Each photoreceptor is a variation of a macromolecule called rhodopsin that has a protein (Opsin) and a photo pigment (Retinal -a Vitamin A derivative) attached to the Opsin.  This photoreceptor is a G protein-coupled receptor that is activated by light and not other chemicals. All that the photon does is change the isomer status of retinal from cis to trans.

The G protein-coupled receptor then undergoes a conformational change with its new energy status. This induces changes in the concentrations of other messengers in cell signalling (like GTP and GMP).

This alters the amount of sodium rushing into the cell (shuts off sodium channels and decreases the amount of sodium in the rod/cone). The charge across the cell membrane changes initiating a nerve impulse to the brain. The rods are involved in night (low light) vision, also called scotopic vision.  When you move from near darkness to bright light the light intensity goes by a factor of 10 billion! That is the reason why you have to squint or look away.

The cones are involved in colour vision, also called photopic vision. There are only 3 kinds of cones. Each has property of being able to absorb a particular wavelength of the 3 primary colours (red, green and blue). Each cone also absorbs the other 2 wavelengths but with diminshed intensity. The relative numbers of a particular colours cone that fire will determine what colour the brain perceives.

In fact there are no colours only different wavelengths of light. It is your brain that makes the world colourful. Certain animals like the rattle snake have thermal imaging and effectively see in infrared.

Certain insects can see only in the UV range and have a different view of flowers that may appear white to us.

The visual centres of the brain process the various information streaming in from your eyes (dark/light pattern, depth of field, shape recognition, colour, motion etc.). This information is then processed at a number(upto 30) of higher visual centres.  Together these centres make a judgement call (fight, flee, love, eat, drink) on which your life depends.

Evolution of the eye

The one eyed king (From eyespots in euglena to eagle eyes – a bird’s eye view)

The eye has evolved at least 50 times in nature.  Microscopic organisms like euglena have a simple eyespot (which is really a photosensitive spot) that can tell the organism – is it light or dark. This helps it move towards or away from light. It also establishes a synchrony with the earth’s rotation – the circadian rhythm. This gives it a great advantage over those organisms unable to move towards a light source – for photosynthesis..

When the photoreceptor cells of the eyespot deepen into a cup they can begin to sense direction of the light. When the entry point of the cup begins to have a smaller aperture it becomes a pin hole camera that produces an image (albeit a blurry one).

If as in the case of trilobites one can co-opt the services of a crystal like calcite ( calcium carbonate) that was found in abundance in the Cambrian sea floor,  a lens forms that focus the light better and one can begin to enjoy depth perception, and have improved image quality. See the calcite in action http://upload.wikimedia.org/wikipedia/commons/0/09/Crystal_on_graph_paper.jpg.

The Parker hypothesis explains the Cambrian explosion of life as due to the rapid evolution of sight. Sight with movement triggered one of the most profound genetic arms race leading to the diversity of species in the Cambrian world. Predatory birds such eagles have among the sharpest eyesight of all animals, fish eagles are thought to even correct for the difference in the refractive index as light passes from air into water.

Add a cornea to the lens and a variations in rhodopsin (the photoreceptor cell) you have the cones and colour vision.

There is a place on the back of your retina called the macula – rich in cones, but no rods and very little blood vessels that produces the best image the eye can produce. When something catches your interest, signals from the brain correct your body position, the position of your head and eyeballs to ensure that the photons from this object stream into the macula.

Colour by numbers

Synaesthesia is a condition that evokes a colour association for a number. The eminent neuroscientist V.S Ramachandran in his excellent book The Tell-tale Brain describes it as a ‘surreal blending of sensation, perception and emotion’. This may be due to possible genetic mechanisms that lead to cross activation in areas of the brain that deal with colour perception and number recognition. These areas lie quite close to each other. There is a hope that the study of this condition may unlock some of the mysteries of the ‘higher functions’ of the brain like perception of self and consciousness.

Artificial eyes

There are at least 15 different large interdisciplinary groups working to produce artificial eyes. One such uses a sub retinal implant of a photovoltaic cell. http://www.stanford.edu/~palanker/lab/retinalpros.html

A short and excellent video explaining the evolution of the eye http://www.wimp.com/eyeevolution/

All you need is love

There is always some madness in love. But there is also always some reason in madness – Friedrich Nietzsche

No single emotion has been written about as much as love. But is it as incomprehensible, deserving of the mystique surrounding it. It has been argued if too much is understood it would lose its charm. I do not agree, the more one understands the scientific underpinning of the thing called love, its beauty is actually enhanced.

So what is this thing called love?

It’s complicated, but I guess you knew that ……romantic love has three components, sexual attraction, emotional attachment and care giving. Each of these gets expressed to varying degrees in different species and in individuals of the same species. Both romantic love and maternal love evolved for one purpose, the propagation of the species.

War creates love

To understand love deeply we have to take a small detour and understand war (biological warfare at any rate).
Germs kill us and have been doing so since multicellular life evolved on the planet. One view of life could be seen as the arms race between certain kinds of microbial (unicellular) life and multicellular organism (humans included). We have even formed alliances with certain bacteria and fungi that live in and on us and protect us from our would be killers.
Our immune system plays a big role in preventing us from being swamped by deadly microbes (bacteria, viruses and fungi), but the arms race implies that the microbes keep changing to avoid surveillance by our immune system.

Love me to protect our children

The immune system broadly needs to do 2 things

1. Make sure that it can recognize your cells from cells that are not yours.
2. Make sure it can recognize as many harmful (to you) cells as possible.

Biology spends a lot of effort to do the above. On your chromosome 6 lies complex of genes that are responsible for this detection of self from non self. It is called the MHC (major histocompatibility complex). While you are in your mother’s womb your immune system learns to recognize what your cells look like and stores that in memory, so it does not attack your cells. The second part of its function (to make sure it attacks as many microbes that are harmful) is actually a skill that is bestowed upon it by both your parents (yes, that’s one more thing you can blame on your parents).

One man’s (or woman’s) stench is another man’s perfume

The more unlike (dissimilar) the MHC is between your father and mother the greater is your range of immunity against diseases. So one of the main basis of mate selection is dissimilarity of MHC complex. So how do you know that a potential mate has a dissimilar MHC?  In two words BODY ODOUR. If the body odour (this is actually produced by the action on your sweat which is odourless by resident bacteria in your skin) of a potential mate is pleasing and not revolting chances are that MHC is dissimilar.

So instead of using gotra and caste based decisions for mate selection – one could just arrange a marriage based on mutual sniffing of armpits. It may be more biologically correct even if a bit short on dignity. It may help reduce the incidence of honour killings in any case.

The other main aspect of sexual attraction is beauty or facial symmetry. There is a significant overlay of cultural, social and financial considerations in human societies on what constitutes sexual attractiveness but peel away the layers and facial symmetry appears to be fundamental.

Facial symmetry denotes MHC similarity not dissimilarity. It appears as in virtually every aspect of biology (indeed the universe itself) this is another example of a trade-off. You want genetic diversity at the MHC complex, but also some convergence on species specific survival trait (like ability to hunt or run away from predators etc.).

Do I eat you or make love to you?

Consider the fact that whether you are prey or predator, most of your life is spent in a state of constant fear or aggression. When you want to have sexual intercourse you have to overcome these basic, life preserving, survival instincts. So how does nature pull of this seemingly impossible- to- overcome contradiction?

In short it suspends rational, critical thinking and rewards irrationality (madly in love is not just poetic). Being truly in love then (neurobiologically speaking) is suspending any kind of judgement on your partner with complete reciprocity – 2 bodies’ one soul.

There are parts of the brain* that are responsible for critical thinking, risk assessment which in essence involves imagining what your enemy would do (you do need empathy to survive).

There are parts of your brain that control or rather promote aggression and violence.

There are parts of the brain that promote sexual arousal.

There are parts of your brain that make you feel happy, content and at ease with the world – the reward centres. This part is closely associated with all forms of addiction.

They all lie in close proximity to one another – sex and violence are only a hair breath away from each other. All are brought into play for the thing called love.

As I had mentioned in a previous blog, cells communicate through chemicals (hormones) or electrical impulses (nerves). In the brain they do both in concert with mind boggling complexity. The chemicals of interest are oxytocin, vasopressin and dopamine.

Very specific to the early stages of falling in love and intensity of feelings is a chemical called nerve growth factor. This factor goes down when you have fallen out of love or have formed a stable relationship (a cynic might say they are the same thing).

The early stages also show an increase in dopamine and decrease in serotonin that mirrors those who have an obsessive compulsive disorder. The analogy of a person in love and an obsessive is not superficial. Nature wants you to pay attention to your potential mate to the exclusion of everything else, that includes not eating in some animals.

In essence once you have seen and smelt your mate and have made an unconscious decision based on MHC compatibility, there is a rush of the above chemicals which stimulate your reward centres, you drop your guard (if you were a T-Rex or Tiger and you don’t, you may ending up killing and eating instead of making love), in tandem with the stimulation of reward centres is an inhibition of both the areas of critical thinking and aggression. Tigers become pussy cats.

Something very interesting happens. Only the visual image of the mate (or ones progeny in the case of the mother) inhibits the aggression centres. Aggression to other males of the species is actually heightened (‘keep your hands off my gal”).

There is significant overlap of romantic love and maternal love pathways in the brain with the exception that the sexual arousal pathways are inhibited in maternal love.

It is not by chance that all these areas in the brain (the reward centres) have a rich supply of oxytocin and vasopressin receptors. One interesting point is in a small mammal called the vole. One type (the prairie vole) is in general monogamous while another (the montane vole) is promiscuous. The difference is in oxytocin receptors in the reward centres of the brain.
In a futuristic world a woman could assess the oxytocin receptor density before saying yes (but that would be no fun – am I right?)

A broader view of love – Other kinds of love

If one extends the concept of love to include bonding a broader picture emerges. Let me explain myself.
Think of it as one, two or more entities (I use the term advisedly) who bond and may or may not have a projection of themselves and a collaboration of themselves for the present and into the future.
The said entities should be bound (or feel they can be bound) in space (newtonian, einstenian or quantum) and time (present and for the future). That view kind of takes the zing out of ‘love’. but it does bring a whole lot of other phenomena under the umbrella of love. The term bond (sounds more solid) and love (sounds more ethereal) can be interchanged, I have a few examples – you may be able to come up with more.

Love between electrons – the covalent bond
Electrons all want a stable relationship and hate being alone (unpaired). The reason there are so many compounds from so few elements is because of this property. For a detailed description see my earlier blog on water. https://paulramesh.wordpress.com/2014/01/05/water-nectar-of-the-gods/

Love between bacteria methanogens and proteobacteria (endosymbiosis)
If a symbiosis between these two bacteria had not developed – a mutual need – there would be no complex life on earth at all. See blog on a marriage made in hell.https://paulramesh.wordpress.com/2013/12/07/a-marriage-made-in-hell-that-created-heaven-on-earth/

Love between plants and animals (photosynthesis and cellular respiration)
Animals need plants to use sunlight to make food and release oxygen and plants need animals to use the oxygen to breakdown the food to release carbon dioxide.

Love between members of a species (the social group)
Many mammals and virtually all primates live in large groups. It helps protect them, easier to hunt for food and preserves genetic heterogeneity. To be cohesive they need to understand each other’s needs. Empathy is a very important trait in primates and may have been the beginning of higher conscious thought.

Love between the members of a hunting pack (male bonding)
Whether it is a pack of wolves, Masai hunters, or a commando unit – a hunt in general is a precarious undertaking and could result in death. Each member of the pack has to trust that they all have the same endpoint in mind. The establishing of male bonding in pack hunters is essential to survival of the individual and the survival of the pack.

The highest love? – Altruism in biology
One of the basic tenets in all religions is that altruism is intrinsically human and connects us to God. I am sorry to disappoint the theists, but not only is it widespread in the natural world, it has an evolutionary significance. If you have grown up fed on a diet of evolution that overemphasised the survival of the fittest dictum, it may surprise you that examples of altruism abound in the natural world.

Multi cellularity itself is altruism on the part of the cells that have chosen mortality over immortality. See blog on the rise of multicellularity.https://paulramesh.wordpress.com/2013/12/21/one-for-all-and-thats-about-it-rise-of-the-multicellular-world/

Dolphins, chimps, dogs, insects all display altruistic behaviour. Humans like all primates are intensely social animals. Cohesion in primate social group has as its basis a give and take policy, further there is evidence that reward centres in the brain are activated with altruism (so altruism may not be completely unselfish).

So for many things it appears …….love is all you need.

The following is an outline – I suggest you read the excellent review by Zeki (from which I have drawn) for a fuller understanding
Zeki.S, The neurobiology of love.FEBS Letters 581 (2007) 2575–2579

*Maternal love but not romantic love – stimulates periaqueductal (central) gray matter (PAG).
In romantic love but not maternal love – stimulates hypothalamus (arousal centres).
In both maternal and romantic love:
Activation of reward centres – (e.g. anterior cingulate and striatum) and the medial prefrontal cortex.
Deactivation (inhibition) during ‘being in love’ – cerebral cortical areas (middle prefrontal, inferior parietal and middle temporal cortices mainly in the right hemisphere, as well as the posterior cingulate cortex). These play an important role in cognition (attention, short- and long-term memory).  Also deactivated are (amygdala, parietotemporal junction and mesial prefrontal cortex). These areas are associated with negative emotions (fear, aggression) and to improved social risk assessment (‘being on your guard’).