Fish

‘Fish’ is one of my favourite words. Having only a single syllable means it can be dropped into conversation without a second thought, thus enabling one to cause maximum confusion with minimal time spent considering one’s move, which often rather spoils the moment. The very… forward nature of the word also suits this function- the very bluntness of it, its definitive end and beginning with little in the way of middle to get distracting, almost forces it to take centre stage in any statement, whether alone or accompanied by other words, demanding it be said loud and proud without a trace of fear or embarrassment. It also helps that the word is very rarely an appropriate response to anything, enhancing its inherent weirdness.

Ahem. Sorry about that.

However, fish themselves are very interesting in their own right; and yes, I am about to attempt an overall summary of one of the largest groups in the animal kingdom in less than 1000 words.  For one thing, every single vertebrate on the planet is descended from them; in 1999 a fossil less than 3cm long and 524 million years old was discovered in China with a single ‘stick’ of rigid material, probably cartilage, running down the length of its body. It may be the only example ever discovered of Myllokunmingia fengjiaoa (awesome name), but that tiny little fossil has proved to be among the most significant ever found. Although not proven, that little bit of cartilage is thought to be the first ever backbone, making Myllokunmingia the world’s first fish and the direct ancestor of everything from you to the pigeon outside your window. It’s quite a humbling thought.

This incredible age of fish as a group, which in turn means there are very few specimens of early fish, has meant that piscine evolution is not studied as a single science; the three different classes of fish (bony, cartilaginous and jawless, representing the likes of cod, sharks and hagfish respectively- a fourth class of armoured fish died out some 360 million years ago) all split into separate entities long before any other group of vertebrates began to evolve, and all modern land-based vertebrates (tetrapods, meaning four-limbed) are direct descendants of the bony fish, the most successful of the three groups. This has two interesting side-effects; firstly that a salmon is more closely related to you than to a shark, and secondly (for precisely this reason) that some argue there is no such thing as a fish. The term ‘fish’ was introduced as a coverall term to everything whose lack of weight-bearing limbs confines them to the water before evolutionary biology had really got going, and technically the like of sharks and lamprey should each get a name to themselves- but it appears we’re stuck with fish, so any grumpy biologists are just going to have to suck it.

The reason for this early designation of fish in our language is almost certainly culinary in origin, for this is the main reason we ever came, and indeed continue to come, into contact with them at all. Fish have been an available, nutritious and relatively simple to catch food source for humans for many a millennia, but a mixture of their somewhat limited size, the fact that they can’t be farmed and the fact that bacon tastes damn good meant they are considered by some, particularly in the west (fish has always enjoyed far greater popularity in far eastern cultures), to the poor cousins to ‘proper meat’ like pork or beef. Indeed, many vegetarians (including me; it’s how I was brought up) will eschew meat but quite happily eat fish in large quantities, usually using the logic that fish are so damn stupid they’re almost vegetables anyway. Vegetarians were not, however, the main reason for fish’s survival as a common food for everyone, including those living far inland, in Europe- for that we can thank the Church. Somewhere in the dim and distant past, the Catholic Church decreed that one should not eat red meat on the Sabbath day- but that fish was permitted. This kept fish a common dish throughout Europe, as well as encouraging the rampant rule bending that always accompanies any inconvenient law; beaver were hunted almost to extinction in Europe by being classed as fish under this rule. It was also this ruling that lead to lamprey (a type of jawless fish that looks like a cross between a sea snake and a leech) becoming a delicacy among the crowned heads of Europe, and Henry I of England (third son of William the Conqueror, in case you wanted to know) is reported to have died from eating too many of the things.

The feature most characteristic of fish is, of course, gills, even though not all fish have them and many other aquatic species do (albeit less obviously). To many, how gills work is an absolute mystery, but then again how many of you can say, when it comes right down to the science of the gas exchange process, how your lungs work? In both systems, the basic principle is the same; very small, thin blood vessels within the structure concerned are small and permeable enough to allow gas molecules to move across the gap from one side of the blood vessel’s wall to the other, allowing carbon dioxide built up from moving and generally being alive to move out of the bloodstream and fresh oxygen to move in. The only real difference concerns structure; the lungs consist of a complex, intertwining labyrinth of air spaces of various size with blood vessels spread over the surface and designed to filter oxygen from the air, whilst gills basically string the blood vessels up along a series of sticks and hold them in the path of flowing water to absorb the oxygen dissolved within it- gills are usually located such that water flows through the mouth and out via the gills as the fish swims forward. In order to ensure a constant supply of oxygen-rich water is flowing over the gills, most fish must keep swimming constantly or else the water beside their gills would begin to stagnate- but some species’, such as nurse sharks, are able to pump water over their gills manually, allowing them to lie still and allow them to do… sharky things. Interestingly, the reason gills won’t work on land isn’t simply that they aren’t designed to filter oxygen from the air; a major contributory factor is the fact that, without the surrounding water to support them, the structure of the gills is prone to collapse, causing parts of it cease to be able to function as a gas exchange mechanism.

Well, that was a nice ramble. What’s up next time, I wonder…

Why the chubs?

My last post dealt with the thorny issue of obesity, both it’s increasing presence in our everyday lives, and what for me is the underlying reason behind the stats that back up media scare stories concerning ‘the obesity epidemic’- the rise in size of the ‘average’ person over the last few decades. The precise causes of this trend can be put down to a whole host of societal factors within our modern age, but that story is boring as hell and has been repeated countless times by commenters far more adept in this field than me. Instead, today I wish present the case for modern-day obesity as a problem concerning the fundamental biology of a human being.

We, and our dim and distant ancestors of the scaly/furry variety, have spent the last few million years living wild; hunting, fighting and generally acting much like any other evolutionary pathway. Thus, we can learn a lot about our own inbuilt biology and instincts by studying the behaviour of animals currently alive today, and when we do so, several interesting animal eating habits become apparent. As anyone who has tried it as a child can attest (and I speak from personal experience), grass is not good stuff to eat. It’s tough, it takes a lot of chewing and processing (many herbivores have multiple stomachs to make sure they squeeze the maximum nutritional value out of their food), and there really isn’t much of it to power a fully-functional being. As such, grazers on grass and other such tough plant matter (such as leaves) will spend most of their lives doing nothing but guzzle the stuff, trying to get as much as possible through their system. Other animals will favour food with a higher nutritional content, such as fruits, tubers or, in many cases, meat, but these frequently present issues. Fruits are highly seasonal and rarely available in a large enough volume to support a large population, as well as being quite hard to get a lot of down; plants try to ‘design’ fruits so that each visitor takes only a few at a time, so as best to spread their seeds far and wide, and as such there are few animals that can sustain themselves on such a diet.  Other food such as tubers or nuts are hard to get at, needing to be dug up or broken in highly energy-consuming activities, whilst meat has the annoying habit of running away or fighting back whenever you try to get at it. As anyone who watches nature documentaries will attest, most large predators will only eat once every few days (admittedly rather heavily).

The unifying factor of all of this is that food is, in the wild, highly energy- and time-consuming to get hold of and consume, since every source of it guards its prize jealously. Therefore, any animal that wants to survive in this tough world must be near-constantly in pursuit of food simply to fulfil all of its life functions, and this is characterised by being perpetually hungry. Hunger is a body’s way of telling us that we should get more food, and in the wild this constant desire for more is kept in check by the difficulty that getting hold of it entails. Similarly, animal bodies try to assuage this desire by being lazy; if something isn’t necessary, then there’s no point wasting valuable energy going after it (since this will mean spending more time going after food to replace lost energy.)

However, in recent history (and a spectacularly short period of time from evolution’s point of view), one particular species called homo sapiens came up with this great idea called civilisation, which basically entailed the pooling and sharing of skill and resources in order to best benefit everyone as a whole. As an evolutionary success story, this is right up there with developing multicellular body structures in terms of being awesome, and it has enabled us humans to live far more comfortable lives than our ancestors did, with correspondingly far greater access to food. This has proved particularly true over the last two centuries, as technological advances in a more democratic society have improved the everyman’s access to food and comfortable living to a truly astounding degree. Unfortunately (from the point of view of our waistline) the instincts of our bodies haven’t quite caught up to the idea that when we want/need food, we can just get food, without all that inconvenient running around after it to get in the way. Not only that, but a lack of pack hierarchy combined with this increased availability means that we can stock up on food until we have eaten our absolute fill if so we wish; the difference between ‘satiated’ and ‘stuffed’ can work out as well over 1000 calories per meal, and over a long period of time it only takes a little more than we should be having every day to start packing on the pounds. Combine that with our natural predilection to laziness meaning that we don’t naturally think of going out for some exercise as fun purely for its own sake, and the fact that we no longer burn calories chasing our food, or in the muscles we build up from said chasing, and we find ourselves consuming a lot more calories than we really should be.

Not only that, but during this time we have also got into the habit of spending a lot of time worrying over the taste and texture of our food. This means that, unlike our ancestors who were just fine with simply jumping on a squirrel and devouring the thing, we have to go through the whole rigmarole of getting stuff out of the fridge, spending two hours slaving away in a kitchen and attempting to cook something vaguely resembling tasty. This wait is not something out bodies enjoy very much, meaning we often turn to ‘quick fixes’ when in need of food; stuff like bread, pasta or ready meals. Whilst we all know how much crap goes into ready meals (which should, as a rule, never be bought by anyone who cares even in the slightest about their health; salt content of those things is insane) and other such ‘quick fixes’, fewer people are aware of the impact a high intake of whole grains can have on our bodies. Stuff like bread and rice only started being eaten by humans a few thousand years ago, as we discovered the benefits of farming and cooking, and whilst they are undoubtedly a good food source (and are very, very difficult to cut from one’s diet whilst still remaining healthy) our bodies have simply not had enough time, evolutionarily speaking, to get used to them. This means they have a tendency to not make us feel as full as their calorie content should suggest, thus meaning that we eat more than our body in fact needs (if you want to feel full whilst not taking in so many calories, protein is the way to go; meat, fish and dairy are great for this).

This is all rather academic, but what does it mean for you if you want to lose a bit of weight? I am no expert on this, but then again neither are most of the people acting as self-proclaimed nutritionists in the general media, and anyway, I don’t have any better ideas for posts. So, look at my next post for my, admittedly basic, advice for anyone trying to make themselves that little bit healthier, especially if you’re trying to work of a few of the pounds built up over this festive season.

Icky stuff

OK guys, time for another multi-part series (always a good fallback when I’m short of ideas). Actually, this one started out as just an idea for a single post about homosexuality, but when thinking about how much background stuff I’d have to stick in for the argument to make sense, I thought I might as well dedicate an entire post to background and see what I could do with it from there. So, here comes said background: an entire post on the subject of sex.

The biological history of sex must really start by considering the history of biological reproduction. Reproduction is a vital part of the experience of life for all species, a necessary feature for something to be classified ‘life’, and among some thinkers is their only reason for existence in the first place. In order to be successful by any measure, a species must exist; in order to exist, those of the species who die must be replaced, and in order for this to occur, the species must reproduce. The earliest form of reproduction, occurring amongst the earliest single-celled life forms, was binary fission, a basic form of asexual reproduction whereby the internal structure of the organism is replicated, and it then splits in two to create two organisms with identical genetic makeup. This is an efficient way of expanding a population size very quickly, but it has its flaws. For one thing, it does not create any variation in the genetics of a population, meaning what kills one stands a very good chance of destroying the entire population; all genetic diversity is dependent on random mutations. For another, it is only really suitable for single-celled organisms such as bacteria, as trying to split up a multi-celled organism once all the data has been replicated is a complicated geometric task. Other organisms have tried other methods of reproducing asexually, such as budding in yeast, but about 1 billion years ago an incredibly strange piece of genetic mutation must have taken place, possibly among several different organisms at once. Nobody knows exactly what happened, but one type of organism began requiring the genetic data from two, rather than one, different creatures, and thus was sexual reproduction, both metaphorically and literally, born.

Just about every complex organism alive on Earth today now uses this system in one form or another (although some can reproduce asexually as well, or self-fertilise), and it’s easy to see why. It may be a more complicated system, far harder to execute, but by naturally varying the genetic makeup of a species it makes the species as a whole far more resistant to external factors such as disease- natural selection being demonstrated at its finest. Perhaps is most basic form is that adopted by aquatic animals such as most fish and lobster- both will simply spray their eggs and sperm into the water (usually as a group at roughly the same time and place to increase the chance of conception) and leave them to mix and fertilise one another. The zygotes are then left to grow into adults of their own accord- a lot are of course lost to predators, representing a huge loss in terms of inputted energy, but the sheer number of fertilised eggs still produces a healthy population. It is interesting to note that this most basic of reproductive methods, performed in a similar matter by plants, is performed by such complex animals as fish (although their place on the evolutionary ladder is both confusing and uncertain), whilst supposedly more ‘basic’ animals such as molluscs have some of the weirdest and most elaborate courtship and mating rituals on earth (seriously, YouTube ‘snail mating’. That shit’s weird)

Over time, the process of mating and breeding in the animal kingdom has grown more and more complicated. Exactly why the male testes & penis and the female vagina developed in the way they did is unclear from an evolutionary perspective, but since most animals appear to use a broadly similar system (males have an appendage, females have a depository) we can presume this was just how it started off and things haven’t changed much since. Most vertebrates and insects have distinct sexes and mate via internal fertilisation of a female’s eggs, in many cases by several different males to enhance genetic diversity. However, many species also take the approach that ensuring they care for their offspring for some portion of their development is a worthwhile trade-off in terms of energy when compared to the advantages of giving them the best possible chance in life. This care generally (but not always, perhaps most notably in seahorses) is the role of the mother, males having usually buggered off after mating to leave mother & baby well alone, and the general ‘attitude’ of such an approach gives a species, especially females, a vested interest in ensuring their baby is as well-prepared as possible. This manifests itself in the process of a female choosing her partner prior to mating. Natural selection dictates that females who pick characteristics in males that result in successful offspring, good at surviving, are more likely to pass on their genes and the same attraction towards those characteristics, so over time these traits become ‘attractive’ to all females of a species. These traits tend to be strength-related, since strong creatures are generally better at competing for food and such, hence the fact that most pre-mating procedures involve a fight or physical contest of some sort between males to allow them to take their pick of available females. This is also why strong, muscular men are considered attractive to women among the human race, even though these people may not always be the most suitable to father their children for various reasons (although one could counter this by saying that they are more likely to produce children capable of surviving the coming zombie apocalypse). Sexual selection on the other hand is to blame for the fact that sex is so enjoyable- members of a species who enjoy sex are more likely to perform it more often, making them more likely to conceive and thus pass on their genes, hence the massive hit of endorphins our bodies experience both during and post sexual activity.

Broadly speaking then, we come to the ‘sex situation’ we have now- we mate by sticking penises in vaginas to allow sperm and egg to meet, and women generally tend to pick men who they find ‘attractive’ because it is traditionally an evolutionary advantage, as is the fact that we find sex as a whole fun. Clearly, however, the whole situation is a good deal more complicated than just this… but what is a multi parter for otherwise?