Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
The fundamental unit of information is a bit, a single unambiguous question that can beanswered in terms of yes and no. With one bit, you can specify one of two possiblities,two bits specify one of four (yes-yes, yes-no, no-yes or no-no) and in general n bitsspecify one of 2n possibilities
Counting a space as a letter, it takes 5 bits to specify a letter (2 to the fifthpower, 32, is the smallest power of two larger than 26.) Computers typically storeinformation in bytes, or clusters of 8 bits. One byte will specify one of 256possibilities, enough to account for all our letters, numbers, and punctuation marks. Ifwe package information in clumps of two bytes, each unit specifies one of 256 x 256 =65,536 possibilities. That's enough to encode all the world's writing systems, includingChinese.
Bits and bytes were pretty specialized pieces of information when Cosmos was produced.Now everyone with a home computer has some idea what they are. It's easy to identify howmuch space something takes up in a computer. Identifying how much of that information isnecessary to extract the full meaning of something is harder; identifying how much of thatmeaning is significant is harder yet. A written page contains a few thousand bits ofinformation; we can probably eliminate all the a's, an's and the's and most of the vowelswithout sacrificing any real information content. Excess information above what we reallyneed to recover meaning is termed redundancy.
The brute-force way to encode pictorial information is in terms of pixels, or smalldots. This means of storage is extremely redundant and space-consuming. Using this mode ofstorage a picture really is worth a thousand words. We can simplify pictorial informationby identifying large blocks that are all the same color; images stored this way take onlya few per cent of the space of pixel-stored images. Line drawings can be described interms of the beginnings and ends of line segments and can be encoded in even more compactterms.
The information content of genes is easy to calculate. Each rung on the DNA ladderconsists of a pair of nucleotides: cytosine (C) paired with guanine (G) or adenine (A)paired with tyrosine (T). Thus each rung can be one of four possibilities: A-T, T-A, C-Gor G-C; it makes a difference which end is which. Thus each rung on a DNA chain containstwo bits of information.
A virus contains 104 bits of information in its DNA or about one printedpage. A bacterium contains 106 bits or about 100 printed pages. A one-celledanimal, an amoeba, contains 4 x 108 bits; 80 volumes at 500 pages each. Mammalscontain 5 x 109 bits or 1500 volumes at 500 pages each.
What if even genes cannot cope with the data flow? Then we have brains. Incidentally,this is the fundamental fallacy of eugenics; once brains become the principal repositoryof information for a species, genes become less important. In fact it is perfectlypossible to select for good genes but bad brains. George Bernard Shaw was once askedsemi-seriously by a famous beauty if he would be interested in a love affair. "Justthink," she said "imagine a child with my looks and your brains." To whichShaw replied "Yes, but what if it had my looks and your brains?
Many biologists believe that the brain evolved from the inside out and consists ofseveral levels or shells. From oldest to youngest they are:
In addition, the brain has two halves, one of which seems to be connected withintuition,the other with critical analysis. In effect, we have two parallel computersprogrammed for different tasks.
It's natural to suppose that different brain functions occupy different places. We knowsensory and motor functions do, and people with brain damage often undergo personalitychanges. In the 19th century there was a widespread theory, called phrenology, thatclaimed to be able to read personality from the exterior shape of a person's skull, basedon the idea that the skull conformed to areas of growth in the brain. The idea deserves tobe treated a bit more charitably than histories of science typically do; in the totalabsence of understanding of the brain it was at least a plausible hypothesis. However, wenow know it's wrong; the brain stores information in a radically different way.
In a computer, a bit of information has a specific location in space; a transistorconducts current or not; a dot on a diskette is magnetized or not. In the brain, eachneural connection represents one bit: the cell is either transmitting to its neighbor ornot. But in the brain the bits don't stay static; they are constantly moving. Also, itappears that every time a memory is accessed, it is copied. One copy is used for someapplication, say taking a test, and the other keeps on circulating. Thus old orfrequently-accessed memories seem to be stored as multiple copies in many places.
We often hear that even Albert Einstein never used more than a tiny fraction of hisbrain capacity. There are two things wrong with that idea:
Chances are that the data you have created occupies only a tiny part of your computer'sactive memory or disk space. Most of the rest, termed overhead in computerparlance, is the operating system and other software. Similarly, a large part of yourcerebral cortex is used for processing sensory data, especially vision. Also, if youfilled every byte of your computer memory or disk drive with data and software, youcouldn't do anything. You need a large amount of free space for working. In the brain,where information is constantly in motion, this is even more true.
The human record for learning foreign languages is about 40. If we assume a vocabularyof 10,000 words per language (extremely literate) and an average of 10 characters perword, one byte per character, we get 4 megabytes of information. In modern software termsthat's a small file. Even if we assume that ten times as much space is needed to storegrammar, we are still only up to 40 megabytes. In one story, Sherlock Holmes admitted hehad never heard of the Solar System and didn't want to know, on the grounds that it mightcrowd out more useful information. He needn't have worried. Textbook learned informationwill never fill more than a tiny fraction of anyone's brain capacity.
How much information would be needed to record your life completely? Visual informationwould probably account for the vast majority of information recorded. Assume you storevisual information at movie speed, 32 frames per second, and that your brain is as good atcompressing this information as a good computer algorithm. A photograph can be compressedto about 50,000 bytes without losing much content. If you live 100 years, that's 100 x 365x 24 x 60 x 60 or 3.1 x 109 seconds. At 32 frames per second and 50,000 bytesper frame, that's 5 x 1015 bytes or 4 x 1016 bits, about 400 timesthe number of neural connections in the brain. But this is still pretty inefficient datastorage. Most visual scenes don't change very much from one moment to the next. Good videocompression schemes record only the changes from one scene to the next and can compresssome video data by 100 times or more. In reality, of course, your brain deems only a tinyfraction of the information it receives as worthy of recording. A lot of information isrecorded in terms of patterns or templates rather than actual images. This complicatesthings like eyewitness testimony enormously since memories of witnesses are only as goodas the patterns their brains use.
The life form most often suspected of being a non-human terrestrial intelligence iswhales. Whale "songs" are 15-30 min. long, comparable in complexity to shortpieces of classical music, and with about the information content of the Iliad orOdyssey. Whale sounds are rich in 20 hertz frequencies, aboutat the lower threshold of human hearing. A "Deep Sound channel" in the oceansthat conducts low frequencies efficiently means that whales effectively had worldwidecommunication. Ship propellers also emit at 20 Hz and may interfere with whalecommunication. Since the episode was filmed commercial whaling by Norway, Japan, and theformer USSR has diminished still further.
Evolution of cities, like that of organs and organisms, is conservative. Vestiges ofthe past are contained in present. Each new addition must mesh with past structures, andit is common to see restructuring and adaptation of existing systems for new uses. Humansare the only known species to have devised information storage outside of brains -Libraries (and now the Internet) are a communal memory that permits communication acrosstime.
Doubters of evolution pose a good question when they ask "what good is half awing, or half an eye?" The utility of half an eye is obvious - any lightdetection and imaging ability is better than none. How wings evolved is more contentious.Feathers probably evolved as insulating materials that were only later adapted for flight.Small creatures don't need much to improve their aerodynamic capabilities - a mousedropped off a cliff would bounce and walk away - so a small creature with feathers purelyfor insulation might well find improved gliding ability as a fringe benefit. So it'sindeed true that organs need to be useful at every stage of their evolution. The problemis that most critics of evolution who raise this issue are looking for any pretext at allto reject evolution, and they rarely spend any effort trying to figure out alternativeuses for partial features.
Would-be devisers of alternative technologies forget the conservative nature ofevolution. New technologies must mesh with pre-existing systems. This conservatism oftencauses undesirable or obsolete features to persist long after their utility is lost. 35-mmcameras initially used movie film because it was easily available. 35-mm cameras hadsprockets because movie cameras did. Now 35-mm film continues to be made with sprocketholes even though it has long been possible to abandon them, because 35-mm cameras have tobe made to make use of the film, which means the film has to have sprocket holes ..... Anynew automotive technology will have to be compatible with existing autos. Nobody is goingto by an electric or hydrogen-burning auto without a promise that it will be easilyrefueled. The alternative is to create and install a completely new technology all atonce. It has been done, but it's a huge task.
Also, new technologies have to be a distinct enough improvement on the old system to beperceived as a real improvement. A ten per cent improvement in performance rarelycompensates for the trouble of replacing an old system with a new one, and an eventualpayoff in the future has to be very large to compensate for additional costs now.
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Created 13 January 1998, Last Update 12 April 2000