First off: this post isn't going to argue the existence of evolution. The theory of evolution originally proposed by Charles Darwin and extrapolated on by biologists since is a valid and true explanation of natural phenomena. Any creationist explanation (including those purported in Islamic scripture) is at best metaphorical and at worst wrong. The idea of biological evolution far predates Charles Darwin. In fact, it can be traced all the way back to Ancient Greece. Anaximander of Miletus proposed that humans evolved from another species, citing that the "first" man would be a helpless baby, unable to survive on its own, like modern babies. Empedocles brought the idea that life may have come about by accident, an idea that resonates today but was quickly rejected by his contemporaries. Aristotle classified living things into a hierarchical structure, believing that organisms were constructed toward a purpose, something Tusi expands on later. Epicurus came up with the idea of Natural Selection: that organisms exhibit many traits, but only the useful ones can survive and perpetuate. These ideas made their way into European thought through Rome, but the teleological attributes were emphasised until anything resembling the modern evolutionary theory was lost. Eventually, as Europe fell into its dark ages, these texts made their way into Muslim hands, including ibn Khaldun and Nasir adDin Tusi.
Muhammad ibn Muhammad ibn Hasan Tusi has one of the most robust evolutionary hypotheses outside of deductive reasoning. Tusi, an established mathematician, studied the Greek and Roman philosophies, as well as religious texts in order to come to his many explanations about the universe. What's most significant about Tusi's work is how closely it compares to modern scientific theories on the same topics. To illustrate that point, we'll be comparing Tusi's explanations to their modern counterparts. (Side note: quotes are pulled from a review of Tusi's Nasirean Ethics. If you'd like to donate a copy of the actual book, we'd humbly accept the offer)
the early universe
Tusi's evolutionary explanation starts with the creation of the universe. Tusi's universe starts with a vast expanse of particulate matter: "They were equal and similar to each other. None of them had an advantage over the others because all of these particles consisted of a common primary matter." However, although the particles were the same, they were not evenly distributed. "As a result, the balance was damaged, and the essential contrasts began to appear inside this early world. Therefore, some substances began to develop faster and better than others." Here's an explanation of this hypothesis from Stephen Hawking:
According to Tusi, this particulate matter is what all the elements of the universe are made from. For Tusi, that's only four elements: fire, water, air, and earth. And these elements further coalesced into minerals, the minerals into plants, plants into animals and ultimately, humans. From a scientific perspective, we can see that Tusi is explaining concentric processes that exist within our own universe. One example of this process is the role hydrogen plays in our universe. About 75% of the matter in our universe is hydrogen, the simplest of atoms. Through nuclear fusion, like what's in our stars, the hydrogen can combine and turn into helium larger elements. Those heavier elements (like nitrogen, oxygen, and carbon) can further combine, creating molecules, proteins, and even life.
According to Tusi, this is how all matter in the universe is formed: as a permutation of other matter. For Tusi, "a body of matter cannot disappear completely. It only changes its form, condition, composition, colour and other properties and turns into a different complex or elementary matter." This hypothesis was proved later by Mikhail Lomonosov, a Russian chemist and known today as the Law of Conservation of Mass. When Albert Einstein proposed mass-energy equivalence in special relativity, it through a wrench into contemporary ideas of mass conservation. However, in Tusi's hypothesis, energy is an inherent property of matter. Therefore, while Tusi's idea isn't the most correct, given our modern understanding, it still technically fits within Einstein's theory.
Once plants and animals are formed, in Tusi's hypothesis, they continue to change through a form of natural competition. "The organisms that can gain the new features faster are more variable. As a result, they gain advantages over other creatures." In modern biology, these can be behavioural and genetic traits, or as Tusi puts it: "The bodies are changing as a result of the internal and external interactions." Here's a brief overview of how genetic evolution works:
Traits are perpetuated or discarded as a direct result of the organism's environment. For example, if giraffes eat food that's high in trees, short giraffes would soon die off (from not eating enough) and not have the ability to pass on their shortness traits. Organisms would then fit into their environment (i.e. tall giraffes only). This is a state that Tusi calls "perfection", although it doesn't describe the organism being perfect, merely having the tools and abilities to cope with its environment. "Look at the world of animals and birds. They have all that is necessary for defence, protection and daily life, including strengths, courage and appropriate tools [organs]."
While plants and animals evolve physical traits in order to cope with their environment, for Tusi, it's what on the inside that counts. For Tusi, "Animals are higher than plants because they are able to move consciously, go after food, find and eat useful things." Plants have their own defence mechanisms (thorns, poisons, etc) but they can't interact with their environment the way animals can. This, according to Tusi, makes animals better than plants. "First of all," writes Tusi, "the animal kingdom is more complicated [than plants]. Besides, reason is the most beneficial feature of animals. Owing to reason, they can learn new things and adopt new, non-inherent abilities." Animals are better than plants because they can think.
In modern science, the jury is still out on what constitutes conciousness, but Tusi followed in the footsteps of ibn Sina and alSijistani for whom intelligence was considered a divine property inherent in higher order beings (i.e. people). For Tusi, intelligence was an evolutionary trait that trumped all others because it brings organisms closer to God. While Tusi describes the evolution of the universe as an entirely natural process, it's certainly not without direction. And that direction is toward godliness.
One of the massive steps Tusi makes is when it comes to human evolution. Tusi explains that humans evolved from apes and even describes other humanoids. "Such humans live in the Western Sudan and other distant corners of the world. They are close to animals by their habits, deeds and behavior[...] The human has features that distinguish him from other creatures, but he has other features that unite him with the animal world, vegetable kingdom or even with the inanimate bodies." Tusi might be describing actual protohumans, such as homo ergaster and neanderthal, or he could just be racist. Either way, Tusi does make a distinction in his hierarchy between humans and other creatures, but it's not a biological distinction. Instead, the only thing separating humans from other organisms is the intellect, which is divinely bestowed only on humans. While other animals have the ability to think and learn, it's the divine intellect that seperates them from humans.
Tusi probably found this notion in the Encyclopaedia of the Brethren of Purity, and particularly the "Debate Between the Animals and the Humans", where animals and humans meet in order to discuss their natural hierarchy. They conclude that (spoilers) humans are better because they possess divine knowledge, above and beyond any knowledge that animals can possess.
However, Tusi's contemporary Jalaluddin Muhammad Rumi made an argument that all matter in the universe possesses an inherent knowledge of the divine. But we'll write about that later.
A brief explanation of teleology:
Some misconceptions about evolution: