Evolution does not proceed automatically toward greater complexity. Rather, the passing of time simply increases the odds of circumstantial variety. Everyone knows that there exist both humans and single-celled organisms. Both are descendants of the same original ancestor. However, it is false to say bacteria simply 'evolved less.' Today's single-celled organisms just have more in common with our shared ancestor. To bring it closer to home, the same might be said of chimpanzees and Australopithecus. The reason humans may learn much about our own species by observing chimpanzees is not because chimps are more like our shared ancestor than humans are. We share a closer genomic divergence with chimps than with any other species. We probably insult our own intellect more than we insult the chimps when we regard them as less evolved humans.

There are a couple of reasons why we know that the common conception of inherent 'progress' in biological evolution is incorrect. First, it is often the case that genomic descendants are less cellularly complex. The 2008 article in ScienceDaily illustrates how even biologists suffer from Darwistotelian disorder. They were surprised to find fossil evidence indicating that ??'s ancestors were remarkably more complex in ??? But this should be common knowledge by now.
What exactly the ultimate gauge of complexity? Above I already discussed cellular complexity. If they thought about it, most evolutionary biologists might put a vote in for genetic complexity. A genetic mutation that is sustained leads to speciation, and the more time a species exists the more time there is to sustain genetic mutations. An indicator of genetic complexity could perhaps be he number of chromosomes. Therefore, if biological evolution leads inherently toward greater genetic complexity, then the most recently established species would have the most chromosomes. That is decidedly not the case. Humans have 46, while an Indian fern has 1260 chromosomes.
Scientists, of course, rapidly disclaim that the number of chromosomes is relevant to organismal complexity and point out the issue of genetic expression. It is true that many genes are not expressed, but we are far from knowing much about genetic expression in either the fern or the human. And for the purposes of ascribing inherent complexity to evolution, it is irrelevant whether genes are expressed (http://micro.magnet.fsu.edu/cells/nucleus/chromatin.html) http://www.madsci.org/posts/archives/2000-05/959100341.Ge.r.html. Not to give genetic expression short shrift, another indication of complexity could be morphology or some other aspect of an organism that is immediately useful to a phenotype. Presumably, this is what scientists who disavow the relevance of genetic complexity infer is actually significant.
Outside of metaphysical arguments, a cursory analysis of today's biodiversity reveals that there is quite a lot of variance in species' traits that may be useful in immediate existence and even very long term fecundity. Crocodiles ancestors of ??? years ago are quite a lot like today's crocodiles. For as long as ???, they have made good use of electrostatic???? On the other hand, today's crocs are morphologically less complex by virtue of being smaller. Morphological complexity also may not be useful in certain cases, and might ironically undermine the evolution-is-progress perspective further. For example, ??? The in-your-face example, however, is probably the complex human brain. While it is certainly not more physically complex than a whale, dolphin, parrot???, it is the case that our brain is more complex than that of Australopithecus. Australopithecus lived for ??? years. Humans have been around about ?? years, and it appears that our brain is in fact going to be a detriment to our continued existence. Many people might quickly point out that quality of life has increased. But that won't meant much if ?? ozone hole, climate change, deforestation, soil loss, etc. Our brains appear to be facilitating our own extinction. The point is only that 10,000 years is a very small amount of time upon which to make a judgment of the relative usefulness of our complex brain to our own species survival, and the global view of the trend is bleak.

So, hopefully I have rubbed in well that evolution does not imply progress. And evolution also does not imply increasing complexity. Evolution plus time does imply increasing complexity, but it is out of a mathematical probability. We have little reason to believe that the propensity toward organismal complexity is an inherent quality of genetics or the biosphere. Given the entrenchment of this idea that evolution equals more complex, an analogy might help.
Think of the world's biota as a lake. Life is rain constantly falling into the lake. That lake is the population of life, and it's simple round shape represents organismal simplicity. As the rain continues to fall, the lake grows. The global population of life grows. Now think of that lake at the top of a mountain. The mountain's height represents time, and the higher the mountain the more time passes. The overflowing lake represents genetic drift. As the water begins to spill down the mountain, it forms little streamlets, then springs, then rivers. Streamlets tend to be at the top, but new ones form out of rivers and ponds as the water descends the mountain. Each body of water is a new species, the shape of which is determined by the topography of the sides of the mountain. As with the the lake bed at the top, the topography of the mountain influences where the water flows. Topography represents genomic inertia [CITATION]. Obviously, the higher the mountain the more bodies of water will form, and the more rivers will form at the bottom. Because the rain is constantly falling (maxim: life exists), there is no qualitative aspect of a stream forming at the bottom that makes it more likely to continue to exist.