The very concept of ';lower'; and ';higher'; life forms is meaningless in biology. This is long outdated thinking based on the idea that humans are at the ';top'; of some ';ladder'; ... so ';higher'; means ';more like us.'; (Another word, besides ';ladder';, to describe this outdated thinking, is the word ';chain'; ... which is where people get the equally outdated concept of ';missing link.';)
Instead, biologists recognize that evolution is not a ';ladder'; or ';chain'; but a constantly branching *bush* (or tree). Species don't *just* become ';higher'; species ... a species can also branch into two separate species (i.e. that can no longer interbreed), which can then can continue evolving in two very different ways. And either or both of these can branch again (or go extinct), and so on.
Humans are just another branch on that bush ... and there is absolutely no reason to think that other branches have not also continued to evolve just as we have, to become the modern species we see today. In other words, a modern chimpanzee is not some sort of ';unevolved human'; frozen in some primitive state of evolution on its way to becoming ';more like us'; ... a chimp is not a ';lower'; life form. It is a fully evolved chimp ... a separate branch that has evolved into the species we see today.
So when asking a question that starts ';If the theory of evolution is true ...';, you need to understand what the theory actually says. If you don't understand *branching*, then you don't understand evolution. If you do understand *branching*, then questions like this (and all variations, like ';why are there still monkeys/apes?';, ';why don't we see monkeys turning into humans?';, ';why haven't all apes become human?';, etc.) are trivially easy to answer.If the theory of evolution is true, why haven't all the lower life forms evolved into higher forms?
Woo hoo. 11 votes is a lot in the Biology section. And many kind words in other answers. My work here is done ... (for today anyway.)
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If the theory of evolution is true, why haven't all the lower life forms evolved into higher forms?
Secretsauce is right on. 'Higher' is not necessarily the same as successful. You could certanly make the argument that countless species of bacteria, or even ants, are at least as successful - and adapted to this world - as homo spaiens are.
Over time species change due to environmental pressures, which is explained by natural selection, becoming more suited to their environment. This tells us that everything over time things will change to be more suited to their environment, not that they will evolve from ';lower to higher forms'; of life.
One way to see this is by looking at many sharks, which have changed little of many many years. They have become well adapted to their environment, and thus have little pressure on them to change.
This can also be easily seen on the Galapagos islands in the many species of finches, one of the sources of Darwin's works. Birds there fell into different niches and over time became more adapted to prosper in that specific niche. They did not change into a higher form of life, just one that was better equipped to meet the pressures of natural selection in their environment.
First, you're looking at an ongoing process and asking why the process isn't finished. It's not finished, because it *is* ongoing. It's kind of like asking: if the theory of aging is true, why isn't everybody old?
Second, nothing in evolutionary theory says a lifeform must evolve. That's just a creationist misrepresentation used to to confuse the issue.
Third, your notion of lower and higher forms is, as Secret pointed out, wonky. Is a more complex organism really a ';higher'; form? Or is the ';higher'; form the one that has the best chance of reproductive success? The one with the longest survival as a species? Plankton has us beat when it comes to reproductive success, which arguably puts them ';higher'; up the ladder than us. Sharks and squirrels have been around much longer than humanity, which arguably puts them ';higher'; up the ladder than us.
Fourth, why do creationists keep asking the same questions over and over but never listen to the answers? Why hasn't their ';lower'; behavior evolved into ';higher'; behavior by now?
JMB
Oh, come on!
Evolution doesnt mean ';lower forms becoming higher forms'; like in a ladder... It means ';forms slightly changing to adapt to their environment, and species branch from each other, thats the reason there are ';lower life forms'; like bacteria which in fact if It wasnt for antbiotics, they would kick your a$$!!
10 pts to secretsauce
You need to study evolution, your question exposes your lack of understanding.
They are already ideally suited to their ecosystems. They are in essence already maxed out.
they all did evolve into higher forms... they were all lower forms at one time just like us.
if the conditions are right, and with enough time, who knows what they will evolve into.
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