On the Inconsistency of the “Suid Gap” Hypothesis and Its Inappropriate Biochronological Use in Dating the Localities of Orce (Venta Micena, Barranco León D, and Fuente Nueva 3). Reply to Martínez-Navarro et al. Comment on “Iannucci, A. The Occurrence of Suids in the Post-Olduvai to Pre-Jaramillo Pleistocene of Europe and Implications for Late Villafranchian Biochronology and Faunal Dynamics. Quaternary 2024, 7, 11”

Abstract

According to the “suid gap” hypothesis, suids (Suidae, Mammalia) would have been absent from Europe between 1.8 and 1.2 Ma. This hypothesis has been influential owing to its putative implications for biochronology and paleoecology—Sus scrofa (the modern wild boar) would appear 1.2 Ma in a period of climatic and environmental changes, coinciding with the beginning of the Epivillafranchian and the Early–Middle Pleistocene Transition, and hominins—the arrival of Homo in western Europe would precede the “return” of pigs. However, the “suid gap” hypothesis is based on the wrong premises that suids are abundantly represented in the European fossil record before and after the “suid gap”, that this purported abundance is linked to the suid reproductive potential, and that the paleontological sites dated within the 1.8–1.2 Ma interval yielded enough remains to exclude the notion that the absence of suid is merely accidental. In a recent paper, it is shown that all these assumptions are erroneous and suid material is described from Peyrolles (France), which is dated at 1.47 ± 0.01 Ma, hence perfectly “filling the suid gap”. Some proposers of the “suid gap” hypothesis have now provided comments to this recent paper, casting doubt on the age of Peyrolles and reiterating the arbitrary statement that suids were commonly recorded and abundantly represented in the Pleistocene of Europe. There is no valid reason to question the homogeneity of the faunal assemblage of Peyrolles, which is indeed a key locality for the mammal biochronology of Europe, being the reference for MNQ 19. Suids of comparable chronology have also been found in Krimni (Greece). Moreover, the “suid gap” proposers are basically advocating the use of an interval biozone based on the temporary absence of Sus strozzii—a species not common in the Pleistocene of Europe—providing no ecological explanation for this gap, apart from speculating it would be due to competition with Homo. The defense of the “suid gap” seems motivated by its use from the “suid gap” proposers as a biochronological argument to contend that the localities of Orce in Spain (Barranco León D, Fuente Nueva 3, and Venta Micena) are older than 1.2 Ma, when they postulated suids would “reappear” in the fossil record. However, since the “suid gap” hypothesis was primarily proposed based on the absence of suids from the Orce sites (and, secondarily, from other sites biochronologically correlated with the localities of Orce, like Pirro Nord in Italy), this represents an evident example of circular reasoning.

1. Introduction

In a recent publication [1], I described suid material from the site of Peyrolles (France; 1.47 ± 0.01 Ma; reference fauna for MNQ 19), using it as a starting point for discussing the rarity of suids in the Early Pleistocene of Europe and how our comprehension of the faunal dynamics of the 1.8–1.2 Ma period is biased by the unequal geographical distribution of sites of this age and the paucity of dating constraints alternative to biochronology. In doing so, the hypothesis of a “suid gap” in Europe in this interval, as proposed by Martínez-Navarro et al. [2], was rejected. Indeed, several authors [3,4,5] already argued that the “suid gap” did not exist, or, if it existed, it had a smaller chronological and/or geographical scope than that proposed by Martínez-Navarro et al. [2]. For instance, suids are recorded in two localities of the area of Krimni, in Greece, which is biochronologically placed at ~1.6–1.5 Ma, just proposed as a representative of a Greek Faunal Unit corresponding to the Italian Faunal Unit of Farneta and Venta Micena in Spain [6], and already correlated with Peyrolles [7]. Based on the suid occurrence at Krimni, Kostopoulos et al. [5] reasoned that either suids were continuously present in southeastern Europe, or the “suid gap” was much shorter there than that in western Europe. Other authors did not recognize any “suid gap” [3] or interpreted it as resulting from a mere lack of documentation [4]. In this regard, it is worth stressing that suids are one of the rarest groups of large mammals in the Pleistocene fossil record of Europe [1], which would indeed make the existence of a “suid gap” in the late Villafranchian, even if verified, most parsimoniously explainable as a taphonomic artifact.

However, some of the proposers of the “suid gap” have now provided comments to my recent paper reaffirming that their hypothesis is correct, reiterating the arbitrary statements on suid commonness and questioning the age of Peyrolles [8]. Here, a reply and critique to the inconsistency of the “suid gap” hypothesis is provided.

Ultimately, the defense of the “suid gap” seems motivated by its use from the “suid gap” proposers as a biochronological argument to contend that the localities of Orce in Spain (Barranco León, Fuente Nueva 3, and Venta Micena) are older than 1.2 Ma, when they postulated suids would “reappear” in the fossil record (e.g., [9,10,11]). However, since the “suid gap” hypothesis was primarily proposed based on the absence of suids from the Orce sites [2] (and, secondarily, from other sites biochronologically correlated with the localities of Orce, like Pirro Nord in Italy), this represents an evident example of circular reasoning.

2. Suid Remains Are Not Common in the Pleistocene Fossil Record of Europe

Martínez-Navarro et al. [2,8] repeatedly affirmed that suids are commonly recorded in Europe before and after the “suid gap”. However, the authors did not provide any evidence to support their claim on the suid commonness, neither in their publication of 2015, nor in their recent comment. Indeed, the main argument to reject the hypothesis of a late Villafranchian “suid gap” is the observation that suids are one of the rarest group of artiodactyls in the Pleistocene of Europe, and, hence, their absence at a given site might easily be fortuitous [1]. In the middle Villafranchian of southwestern Europe (Iberian Peninsula, France, and Italy), suids are known from a few localities that are dated or correlated to ~2.4–2.1 Ma, namely, Valdeganga II in Spain, Saint Vallier and Senèze in France, and Coste San Giacomo, Pantalla, Quercia, and Vigna Nuova in Italy [1,12]. The most abundant of these samples is represented by a mere total of six isolated teeth recovered from Quercia, recently described [12]. Martínez-Navarro et al. [8] ignored this publication, where the paucity of the other middle Villafranchian samples is also pointed out. At Saint Vallier, suids are represented by a single fragmentary deciduous premolar, out of thousands of large mammal remains [13,14]. Senèze is an exceptional locality that yielded almost complete skeletons of several large mammals, one of which belonging to a subadult S. strozzii, and, in any case, it was only one individual [15,16]. Three lower molars have been recovered from Valdeganga II [17], some fragmentary and/or isolated teeth from Coste San Giacomo [18], a single hemimandible from Pantalla [4], and two maxillary fragments from Vigna Nuova [19]. In total, less than twenty suid specimens are known from southwestern Europe for the first ~0.4 Ma of suid documentation in the Pleistocene.

Fonelas P-1 is the only locality in southwestern Europe, among those that have been considered “transitional” between the middle and the late Villafranchian [20], that yielded suid remains [21]. The latter, however, only account for 0.33% of the findings; i.e., there are 10 suid remains out of 3000 specimens recovered from Fonelas P-1 [21,22].

The late Villafranchian localities correlated to the Olivola and Tasso Faunal Units (~2.0–1.8? Ma) document the acme of abundance of suids (S. strozzii) in the Early Pleistocene of southwestern Europe [1]. Data on faunal assemblages available from the literature show that, in terms of the number of occurrences (frequency), suids were present in 57.1% of the localities of this time interval [1]. Therefore, it could be argued that they were moderately common at that time—however, with the important specification that this is only true for the Italian fossil record, because S. strozzii was not present either in France or Spain in this time interval (i.e., the purported “gap” would start after Senèze and Fonelas P-1, respectively). The localities of Olivola and the Upper Valdarno, both in Tuscany (Italy), yielded numerous remains of S. strozzii, including several crania and mandibles [16]. In absolute terms, the suid remains are abundant, but it is difficult to evaluate their relative quantity with respect to the rest of the fauna, which derives from historical collections that are scattered in many museums and institutions. In particular, to consider the Upper Valdarno a single locality is reductive, being a 35 km long and 15 km wide basin from which paleontological remains have been recovered for centuries [16,23,24]. Looking at a single and recently excavated (i.e., not historical) locality of the Upper Valdarno, Poggio Rosso, which is also the only one for which detailed information on the number of identified specimens is available [25], reveals that remains of S. strozzii account for a mere 4% of the total findings.

After the purported “suid gap” (~1.1–1.0 Ma), suids were only present in 37.5% of the localities of southwestern Europe, and, in those localities where they were present, they always constitute one of the rarest groups [1]. The two most abundant Epivillafranchian suid samples are from Untermassfeld [26] and Vallparadís [27]. In both cases, suids are the rarest artiodactyls apart from Capreolus cusanoides at Untermassfeld and Caprini indet. at Vallparadís layer EVT7; in percentage, suids account for slightly more than 1% of the inferred minimum number of individuals or the number of identified specimens [1].

In brief, contrary to what was claimed, with no evidence whatsoever, by Martínez-Navarro et al. [2,8], suids are one of the rarest groups of ungulates in the European fossil record of the Early Pleistocene. This simple and objective fact should be already enough to disregard the biochronological use of the purported “suid gap”.

3. Peyrolles Is a Chronologically Homogeneous Fauna and the Reference for MNQ 19

Since the first half of the 19th century, the area of Peyrolles yielded several remains of large mammals, and the resulting fauna is the reference for the “zone de Peyrolles”, or MNQ 19, in the French biochronological system [7,28]. The paleontological site was rediscovered and excavated during the 1990s, confirming the homogeneous provenance of the fauna from a single fossiliferous layer [7]. The fossil-bearing formation has been dated by multiple methods over the years, with the most precise and accurate estimate being the ⁴⁰Ar/³⁹Ar age of 1.47 ± 0.01 Ma obtained by Nomade et al. [29]. The presence of suid material from the historical collection of Peyrolles has long remained unnoticed, probably because it consists only of an isolated and fragmented metatarsal, but this specimen is nonetheless part of the same homogeneous faunal assemblage which is a reference for the biochronology of western Europe [1].

Martínez-Navarro et al. [8] claimed that the fauna of Peyrolles was recovered from multiple layers, and reported several age estimates that would widen its chronological range. The first argument is simply false and inconsistent with the results of the authors who excavated the site [7]. The second argument is also misleading because, although different age estimates were indeed obtained for the fossil-bearing formation of Peyrolles, these are superseded by the ⁴⁰Ar/³⁹Ar age of 1.47 ± 0.01 Ma obtained by Nomade et al. [29], which is not only more precise and accurate, but also more reliable than previously applied methods (e.g., K-Ar [30]).

Martínez-Navarro et al. [8] also claimed that the age of Peyrolles should be close to 1.8 Ma, owing to the presence of Leptobos cf. etruscus, which would disappear in later chronologies, being replaced by Bison. In support of this claim, they quoted Sorbelli et al. [31], who conversely considered it likely that Leptobos and Bison coexisted for a short period. Indeed, the coexistence of Leptobos and Bison characterizes the Greek Faunal Unit of Krimni [6], correlative to Peyrolles [7]. The presence of Leptobos and Bison has also been recognized at Venta Micena [3].

4. On the Presence of Suids in the Krimni Faunal Unit (~1.6–1.5 Ma), with Remarks on Other Potential Occurrences Within the Purported “Suid Gap”

Apart from Peyrolles, two sites in the area of Krimni (Krimni-1 and Krimni-3) have yielded suid remains [5]. Krimni-1 was already correlated with MNQ 19 (i.e., the zone of Peyrolles) [7] and Konidaris and Kostopoulos [6] recently proposed a series of Faunal Units for Greece, correlating the Krimni FU with the Farneta FU of Italy and Venta Micena in Spain, for which they favored an age of ~1.6–1.5 Ma. Martínez-Navarro et al. [8] ignored the suid presence at Krimni, in the same way they [2] previously omitted to discuss most of the localities with potential suid occurrences that would have debunked the “suid gap” hypothesis [1]. Indeed, simply opting for a different biochronological placement of some localities would result in recognizing a continuous suid presence in Europe, even excluding the records from Krimni and Peyrolles [3]. In their comment, Martínez-Navarro et al. [8] now provided belated considerations on some of the localities I mentioned [1], in several cases introducing misleading or imprecise information. Some remarks are needed, at least for the Mugello Basin and Pirro Nord.

4.1. Mugello

The large mammal findings recovered from the Mugello Basin have been correlated with the Tasso and Farneta FUs and the published information on the suid material are limited only to the presence of S. strozzii from “Pulicciano”, together with Hippopotamus sp. and Mammuthus meridionalis [32]. In their comment, Martínez-Navarro et al. [8] echoed the considerations on the uncertain chronology of the fauna [1], but they used another name for indicating the precise locality of the findings and added information on the suid material which is partially incorrect. Since both aspects might engender confusion in subsequent studies, a comment is needed. I referred to the suid material of the Mugello Basin as being from “Pulicciano” for consistency with the publication of Abbazzi et al. [32], where this name is used, but this material is the same as the one Martínez-Navarro et al. [8] referred to as being from “Ronta” (which is the toponym present on the historical handwritten labels). With regard to the suid material itself, Martínez-Navarro et al. [8] (p. 4) stated that it consists of “two upper M2 permanent teeth, IGF4828V, and one juvenile upper M3, IGF988V”. However, because of the curator Luca Bellucci, we could verify that, among the two specimens catalogued under the number IGF 4828V, only one second upper molar (M2) is present, and it is a fragment. The other specimen with the same catalogue number is a first upper molar (M1). Moreover, the reference to a “juvenile” M3 is a terminological contradiction, considering that third molars are the last permanent teeth to erupt.

4.2. Pirro Nord

In their publication of 2015 [2], Martínez-Navarro, Palmqvist, and collaborators simply stated that suids are not present at Pirro Nord, without any detail of the material they studied, nor any comment on the papers that previously reported the presence of suids from the locality. Indeed, Pirro Nord has been investigated by many institutions over the years, and there are two independent reports of the presence of suids, by Freudenthal [33] and De Giuli et al. [34], the former being based on material recovered during the first fieldworks (1969–1971) and the latter on a sample collected in 1984. In my contribution [1], I simply argued that, before disregarding the presence of suids at Pirro Nord, it would be appropriate to revise the collections from which they are cited, especially considering that the whereabouts of part of the material collected during the early excavations have long been forgotten (the material is in the University of Bari [35]). In their comment, Martínez-Navarro et al. [8] now stated that, during a visit in 2000, two of them (B.M.-M. and L.R.) have revised the collection of the Freudenthal excavations at Pirro Nord housed in Bari. However, only in 2021, several sealed boxes, containing material recovered from Pirro Nord and reporting the indication of international shipping from the Netherlands, were rediscovered in the University of Bari and are now under study within a PhD project (Raffaele Sardella, pers. comm., [35]).

5. The Presence of Suids at Dmanisi

The presence or absence of suids at Dmanisi would have little relevance for the “suid gap” hypothesis, since the site is dated at ~1.8 Ma, concurrently with several other localities with suid remains [1]. However, according to Martínez-Navarro et al. [2], Dmanisi would have been one of the first sites without suids and they put much emphasis on rejecting the presence of suids from Dmanisi, stating that “we can affirm that after a long period of systematic excavations at sites such as Dmanisi, which has provided a huge collection of large mammals remains, including an abundant record of ungulates, carnivores and also hominins, no pigs have ever been found” [2] (p. 136). It is noteworthy that, despite their claim to have provided an “extensive revision of the literature” [8] (p. 1), Martínez-Navarro et al. [2] did not mention that, already in 1995, Vekua [36] described and figured a suid incisor from the site. In their comment [8] (p. 2), they now stated that “Vekua [36] described and figured an upper incisor, I2, ascribed to Sus sp. in Dmanisi, but the occurrence of this species disappeared from the faunal lists published later for the site [37]”. No reason is given for this “disappearance”, despite two of the authors also being involved in the cited research (B.M.-N. and L.R.). Moreover, the attribution to a second upper incisor, endorsed by Martínez-Navarro et al. [8], is erroneous, as the specimen figured by Vekua [36] (plate 39, figure 2) rather represents a suid first upper incisor (or the equivalent milk tooth). Perhaps, this specimen was excluded from subsequent faunal lists because of the doubt stratigraphic provenance [36], but a clarification would be needed.

Further suid material has been recovered from Dmanisi during recent excavations, which, according to Martínez-Navarro et al. [8], includes two specimens. A description of the new and old material would be much welcome, given the importance of Dmanisi and the general rarity of suid remains in the Early Pleistocene of Europe and adjacent areas. In any case, Dmanisi is an emblematic example of why the absence of suids at a given location cannot be considered conclusive, since, after decades of extensive excavation, only two (or three) suid specimens have been recovered out of 2764 identified remains [38]. This means that suids at Dmanisi are present, but account for less than 0.01% of the total of the findings.

6. A High Reproductive Potential Does Not Translate to a High Number of Fossils

In their publication of 2015, Martínez-Navarro et al. [2] did not provide any arguments to support their unsubstantiated claim that a high reproductive potential should result in an abundance of remains in the fossil record. In their comment, they now exposed their reasoning, arguing that, “in a fossil assemblage taphonomically unbiased, the abundance of skeletal remains for a given mammalian species would exclusively depend on the number of individuals that died while the assemblage was being formed. In this way, the relative abundance of each species can be estimated as a function of its mean population density in the paleocommunity” [8] (p. 5). However, to take this as an argument in favor of their hypothesis would imply assuming that all the localities falling within the purported “suid gap” are “taphonomically unbiased” and that the “mean population density” solely depends on the reproductive strategy of a mammal. At the very least, where an “assemblage was being formed” is a crucial aspect to consider, as what species could or could not be present or be abundant ultimately depends on it. For instance, the remains of Late Pleistocene cave bears are extremely abundant not because cave bears developed a peculiar reproductive strategy, but because of their habit of using caves, and because caves with Late Pleistocene deposits are abundant in the first place (e.g., [39]). Looking at the artiodactyls in the late Early Pleistocene of Europe, we see the hippopotamuses were very abundant in terms of the number of occurrences (they occurred in 75% of the localities in the ~1.1–1.0 Ma interval [1]), and, when present, they were often among the most represented species at a given site. However, this has nothing to do with the reproductive potential of hippopotamuses, but it is probably primarily related to their ethology, which makes their remains often highly represented in fluvio-lacustrine settings, perhaps synergically aided by the large size of their remains.

With regard to the “mean population density”, the reasoning of Martínez-Navarro et al. [8] denotes a complete misunderstanding of the r/K selection theory, which they called upon as an explanation. First, although the r/K selection theory represents one of the most important concepts in the study of life-history evolution, its use as a predictive model is long surpassed (e.g., [40]). Second, even staying within the r/K selection conceptual framework, r-selected species are not expected to constantly have larger populations than K-selected species, but they are rather characterized by sharp demographic fluctuations [41]. Of course, a population of an r-selected species can grow very rapidly, but only when favorable conditions occur (e.g., an increase in trophic resources, reduced predation, and an introduction into a new territory). In other words, even assuming a high population density would always correspond to a high abundance in the fossil record (which is not the case), there would be no reason to predict a high abundance of suids at a given site, unless having specific evidence for the existence of conditions peculiarly favorable to the growth of suid populations.

7. The “Return” of the Pigs Is Not Related to the Extant Wild Boar, Sus scrofa

A key element to convey the idea of Martínez-Navarro et al.’s [2] “suid gap” hypothesis was the purported identification of the Epivillafranchian (i.e., post-1.2 Ma) suids as belonging to a species phylogenetically related to the extant wild boar (Sus gr. scrofa). Indeed, S. scrofa is an extremely adaptable species, hence serving to Martínez-Navarro et al. [2] as a perfect herald of the paleoenvironmental changes of the Early–Middle Pleistocene Transition and as a suitable biochronological marker of the Epivillafranchian. In their paper of 2015, Martínez-Navarro et al. [2] did not provide any clear detail of the suid material they revised. In their comment [8] (p. 2), they now clarified that they were “aware of the hotly debate around the adscription of the Epivillafranchian newcomer form, and decided to cite it as Sus gr. scrofa”. Basically, they admitted that their attribution of the post-1.2 Ma suids to S. scrofa was not based on a systematic paleontological assessment of the material, but merely represented an arbitrary choice. Not even a year after Martínez-Navarro et al. [2] published the “suid gap” hypothesis, Bona and Sala [42] described suid material unequivocally not belonging to S. scrofa (assigned to S. strozzii) from the locality of Frantoio (Italy), placed at the top of the Jaramillo subchron—hence, ~0.99 Ma. In subsequent publications, Martínez-Navarro, Palmqvist, and collaborators completely ignored Bona and Sala’s [42] work, reiterating the view that, after 1.2 Ma, S. scrofa was the suid species present in Europe (e.g., [10]). They also systematically ignored the work by Van der Made et al. [3], where the authors, apart from rejecting the existence of a “suid gap” altogether, referred several late Early Pleistocene samples to Sus sp. or S. strozzii. This lasted until the publication by Cherin et al. [27]—who also involved one of the “suid gap” proposers (J.M.-M.)—in which the “return” of the suids was interpreted as a persistence of S. strozzii (i.e., the same species present before the purported “suid gap”). It is worth noting that the temporary absences of large mammal species recorded before and after, but not during, a certain time interval are commonly interpreted in the Pleistocene of Europe as due to a lack of documentation, sometimes even used to compare the “quality” of the fossil record between different areas, and certainly never used as a stand-alone biochronological argument [43,44]. Nevertheless, despite accepting the attribution to S. strozzii of the Epivillafranchian suids, Martínez-Navarro, Palmqvist, and colleagues [8,11] insisted on defending the “suid gap” hypothesis, basically advocating the use of an interval biozone—which would be the only case for a large mammal in the Pleistocene of Europe—based on one of the rarest artiodactyl species.

8. Other Remarks

There are several other imprecisions in the work of Martínez-Navarro et al. [8], of which a couple of significant examples are listed below:

• Martínez-Navarro et al. [8] (p. 5) stated that “Suidae is the only family of the Old World ungulates that has developed a truly r reproductive strategy”.
  There is no such thing as a “truly r reproductive strategy”; the r/K selection theory is a generalization of an ecological continuum [41]. Moreover, suids have only some of the characteristics normally considered typical of r-selected species; for instance, their longevity and body mass are typical for K-strategists [1,41]. It is exactly this uncommon combination of features that makes suids unique [1]. Finally, suids did not develop an r-strategy deviating from the other ungulates, but, rather, retained it as many other “primitive” characteristics of their anatomy and biology, though some suids (Sus) probably specialized further in the direction of the rapidity of reproduction [1].
• Martínez-Navarro et al. [8] (p. 5) stated that “the remains of juvenile pigs, especially teeth, use to be relatively abundant in the fossil collections. Among others, this is the case of the Epivillafranchian suid from the site of Dunaalmás, Hungary”.
  Dunaalmás yielded the only confirmed occurrence of S. strozzii from Hungary published so far, consisting of one mandibular fragment with a deciduous fourth premolar [45]. This is one single specimen for an entire country, and, hence, another evident example of the rarity of Pleistocene suids in the European fossil record. Moreover, although the age of the finding is uncertain, in the quoted publication [45], it is assigned to the late Villafranchian, with an estimated age of ~2.0–1.5 Ma, and not to the Epivillafranchian, as wrongly reported by Martínez-Navarro et al. [8]. Finally, the statement that remains of juvenile suids are abundant in the fossil collections is another arbitrary claim. The most abundant sample of juvenile suid remains from the Early Pleistocene of Europe known to date is from Untermassfeld, where there is only one skull and few isolated teeth out of thousands of fossils recovered from the site [26].

9. Discussion and Conclusions

In its current formulation [8,11], the “suid gap” would be an interval biozone based on the temporary absence of S. strozzii, one of the rarest artiodactyls in the Pleistocene fossil record of Europe, and the only reason for its absence between 1.8 and 1.2 Ma would be the speculative competition with Homo. To support the “suid gap” hypothesis, it would also be necessary to disregard the occurrences of suids from Peyrolles and Krimni at ~1.5 Ma. From these premises, it is evident that the “suid gap” hypothesis must be refused, and, indeed, apart from the publications in which the “suid gap” proposers are authors, all other studies specifically discussing the subject did not agree with Martínez-Navarro et al. [2]. Van der Made et al. [3] rejected the existence of a “suid gap” altogether. Cherin et al. [4] argued that the “suid gap” might be interpreted as a mere lack of documentation. Kostopoulos et al. [5] suggested that either the “suid gap” had a much shorter duration than that previously proposed or suids were continuously present, at least in the Balkans. Eventually, I simply emphasized more explicitly than other researchers the inconsistency in the reasoning of Martínez-Navarro et al. [2], especially given the rarity of suids in the Pleistocene fossil record of Europe and the paucity of paleontological sites dated within the purported “suid gap” [1].

Over the years, Martínez-Navarro, Palmqvist, and colleagues systematically ignored all evidence challenging their claims (e.g., the presence of suids at Dmanisi known since the 1990s [36]; and the identification of S. strozzii from Frantoio at ~0.99 Ma [42]). They did not present any data to disprove the main weakness of the “suid gap” hypothesis (i.e., the rarity of suids), but, rather, tried to divert the discussion towards the age of Peyrolles and misleadingly undermine its reliability—which would have a wider detrimental effect for the biochronology of Europe, considering the paucity of localities available. They even tried to include in the acknowledgements of their comment my former PhD supervisor, Raffaele Sardella, alongside other researchers (none of which is present in the final published version of their comment), for having provided “some bibliographic data that helped to support the discussion”, in a subtle attempt to make it appear that their conclusions are supported by other researchers. Certainly, this is not the case for Raffaele Sardella, who did not give his consent to be mentioned in the acknowledgements in the published version of the comment (Raffaele Sardella, pers. comm.).

It is evident that Martínez-Navarro, Palmqvist, and colleagues are stressing the existence of a “suid gap” in order to support an age older than 1.2 Ma for the Orce sites of Venta Micena, Barranco León D, and Fuente Nueva 3. Yet, it is worth noting that they proposed the “suid gap” hypothesis based on the absence of suids from these very same sites, in a clear example of circular reasoning. Indeed, the available numerical ages for the Orce sites without suids do not provide any conclusive indication they would actually fall within the purported “suid gap” chronology [46,47,48]. This is not to say that the Orce sites are certainly younger than 1.3–1.2 Ma, but, simply, that the absence of suids is not a reliable biochronological argument to support an older age.

As argued before [1], the case of the “suid gap” highlights how little we know about the critical timespan between the earliest occurrence of Homo outside Africa and its appearance in the European fossil record. In the meantime, the results of a multi-technique dating approach applied to Pirro Nord have been published, with numerical ages clustering at ~0.8 Ma, substantially challenging previous estimates (1.7–1.3 Ma) [48]. The faunas of Pirro Nord and Venta Micena share a large number of similarities, supporting the view that they are close in age, and both slightly older than those from Barranco León D and Fuente Nueva 3 (e.g., [49]). The ~0.8 Ma estimate for Pirro Nord might be tentatively considered a minimum age for the fauna and lithics, assuming some reworking of the material with respect to the hosting sediment [48]. However, this would not be supported by previous taphonomic analyses [50], and, therefore, if some reworking occurred, it is hardly conceivable that it could account for a discrepancy of more than 0.5 Ma. If Pirro Nord is younger than previously assumed, by extension, Venta Micena, Barranco León D, and Fuente Nueva 3 cannot be as old as promoted by Martínez-Navarro, Palmqvist, and colleagues (i.e., 1.6–1.4 Ma). Indeed, several researchers favored a younger age for these sites (i.e., 1.3–1.2 Ma), either purely based on divergent biochronological interpretations (e.g., [3,51]) or other methods (e.g., [52]). Hopefully, future dating attempts might refine these chronological attributions.

A frank discussion aimed at reconciling paleontological and geochronological evidence is now timely, and this can only be possible if new data are published and discussed with an open mind. If nothing else, I hope this exchange of comments and reply helps fuel the research and interest in suids, which remain one of the rarest and least studied groups of large mammals in the Pleistocene of Europe, and especially promotes the description of new material.