People who are advocates to the theory of evolution are already believers in the intelligent design. By definition evolution itself is an intelligent design. According to Douglas Theobald, Ph.D. www.talkorigins.org "In spite of the extensive variation of form and function among organisms, several fundamental criteria characterize all life. Some of the macroscopic properties that characterize all of life are (1) replication, (2) heritability (characteristics of descendents are correlated with those of ancestors), (3) catalysis, and (4) energy utilization (metabolism). At a very minimum, these four functions are required to generate a physical historical process that can be described by a phylogenetic tree."
He attributes however this design to a common descent. According to Dougals "
If every living species descended from an original species that had these four obligate functions, then all living species today should necessarily have these functions (a somewhat trivial conclusion). Most importantly, however, all modern species should have inherited the structures that perform these functions. Thus, a basic prediction of the genealogical relatedness of all life, combined with the constraint of gradualism, is that organisms should be very similar in the particular mechanisms and structures that execute these four basic life processes."
He confirms his hypothesis by the discovery of the same biochemical that serve these structures" The structures that all known organisms use to perform these four basic processes are all quite similar, in spite of the odds. All known living things use polymers to perform these four basic functions. Organic chemists have synthesized hundreds of different polymers, yet the only ones used by life, irrespective of species, are polynucleotides, polypeptides, and polysaccharides. Regardless of the species, the DNA, RNA and proteins used in known living systems all have the same chirality, even though there are at least two chemically equivalent choices of chirality for each of these molecules. For example, RNA has four chiral centers in its ribose ring, which means that it has 16 possible stereoisomers—but only one of these stereoisomers is found in the RNA of known living organisms."
The common descent theory is strengthened by the discovery of DNA and RNA. According to Douglas " Ten years after the publication of The Origin of Species, nucleic acids were first isolated by Friedrich Miescher in 1869. It took another 75 years after this discovery before DNA was identified as the genetic material of life (Avery et al. 1944). It is quite conceivable that we could have found a different genetic material for each species. In fact, it is still possible that newly identified species might have unknown genetic materials. However, all known life uses the same polymer, polynucleotide (DNA or RNA), for storing species specific information. All known organisms base replication on the duplication of this molecule. The DNA used by living organisms is synthesized using only four nucleosides (deoxyadenosine, deoxythymidine, deoxycytidine, and deoxyguanosine) out of the dozens known (at least 99 occur naturally and many more have been artificially synthesized) (Rozenski et al. 1999; Voet and Voet 1995, p. 969).
Moreover, the functions of organisms are through enzymatic catalysis of proteins that constructed from same subset of 22 amino acids " In order to perform the functions necessary for life, organisms must catalyze chemical reactions. In all known organisms, enzymatic catalysis is based on the abilities provided by protein molecules (and in relatively rare, yet important, cases by RNA molecules). There are over 320 naturally occurring amino acids known (Voet and Voet 1995, p. 69; Garavelli et al. 2001); however, the protein molecules used by all known living organisms are constructed with the same subset of 22 amino acids."
According to Douglas "There must be a mechanism for transmitting information from the genetic material to the catalytic material; all known organisms, with extremely rare exceptions, use the same genetic code for this. The few known exceptions are, nevertheless, simple and minor variations from the "universal" genetic code (see Figure 1.1.1) (Lehman 2001; Voet and Voet 1995, p. 967), exactly as predicted by evolutionary biologists, if common descent were correct, years before the genetic code was solved (Brenner 1957; Crick et al. 1961; Hinegardner and Engelberg 1963; Judson 1996, p. 280-281)."
Thus evolution theory advocates are right. Some macroscopic properties characterize all of life. These properties are due to same group of biochemical substances that result from chemical reactions by catalytic enzymes. The later is doing that through a genetic code transmitted by the genetic material.
As you noted it is an intelligent design of evolution. There are also other proofs to suggest a common decent to life. However, life could be due to a common creator who may or may not used the common descent for species or created from similar materials all the species. It is poosible that God did or allowed some genetic mutation to happen to improve survival of species. The encoded DNA the miracle of creation is just very intelligently designed that necessitate a creator behind it. It is like the universe and law of physics too much intelligence that call all of us to believe in a creator.